diff --git a/R/assortativity.R b/R/assortativity.R
index ae9ce17fde4..f2d3dea1c28 100644
--- a/R/assortativity.R
+++ b/R/assortativity.R
@@ -184,7 +184,7 @@ assortativity <- function(
     if (!missing(directed)) {
       dots[["directed"]] <- directed
     }
-    if (missing(values)) {
+    if (is_missing(values)) {
       dots[["types1"]] <- types1
     } else {
       dots[["types1"]] <- values
@@ -192,7 +192,7 @@ assortativity <- function(
     return(inject(assortativity_legacy(!!!dots)))
   }
 
-  if (missing(values)) {
+  if (is_missing(values)) {
     lifecycle::deprecate_warn(
       "1.6.0",
       "assortativity(types1 =)",
diff --git a/R/attributes.R b/R/attributes.R
index 13824155c1c..bb1607a7a0c 100644
--- a/R/attributes.R
+++ b/R/attributes.R
@@ -322,7 +322,7 @@ get.edge.attribute <- function(graph, name, index = E(graph)) {
 graph_attr <- function(graph, name) {
   ensure_igraph(graph)
 
-  if (missing(name)) {
+  if (is_missing(name)) {
     return(graph.attributes(graph))
   }
 
@@ -358,7 +358,7 @@ graph_attr <- function(graph, name) {
 #' )
 #' plot(g)
 `graph_attr<-` <- function(graph, name, value) {
-  if (missing(name)) {
+  if (is_missing(name)) {
     `graph.attributes<-`(graph, value)
   } else {
     check_string(name)
@@ -450,7 +450,7 @@ graph.attributes <- function(graph) {
 #' plot(g)
 vertex_attr <- function(graph, name, index = NULL) {
   ensure_igraph(graph)
-  if (missing(name)) {
+  if (is_missing(name)) {
     if (is.null(index)) {
       return(vertex.attributes(graph))
     }
@@ -504,7 +504,7 @@ vertex_attr <- function(graph, name, index = NULL) {
   if (is.null(index)) {
     index <- V(graph)
   }
-  if (missing(name)) {
+  if (is_missing(name)) {
     `vertex.attributes<-`(graph, index = index, value = value)
   } else {
     check_string(name)
@@ -774,7 +774,7 @@ set_value_at <- function(value, idx, length_out) {
 edge_attr <- function(graph, name, index = NULL) {
   ensure_igraph(graph)
 
-  if (missing(name)) {
+  if (is_missing(name)) {
     if (is.null(index)) {
       edge.attributes(graph)
     } else {
@@ -829,7 +829,7 @@ edge_attr <- function(graph, name, index = NULL) {
   if (is.null(index)) {
     index <- E(graph)
   }
-  if (missing(name)) {
+  if (is_missing(name)) {
     `edge.attributes<-`(graph, index = index, value = value)
   } else {
     check_string(name)
diff --git a/R/community.R b/R/community.R
index 783f7676000..8c0c0806d30 100644
--- a/R/community.R
+++ b/R/community.R
@@ -1323,8 +1323,8 @@ cut_at <- function(communities, no, steps) {
   }
 
   if (
-    (!missing(no) && !missing(steps)) ||
-      (missing(no) && missing(steps))
+    (!is_missing(no) && !is_missing(steps)) ||
+      (is_missing(no) && is_missing(steps))
   ) {
     cli::cli_abort("Please use either {.arg no} or {.arg steps} (but not both)")
   }
@@ -1336,7 +1336,7 @@ cut_at <- function(communities, no, steps) {
   # dedicated igraph_le_community_to_membership function.
   if (isTRUE(communities$algorithm == "leading eigenvector")) {
     n_initial <- max(communities$membership)
-    if (!missing(steps)) {
+    if (!is_missing(steps)) {
       if (steps > nrow(mm)) {
         cli::cli_warn("Cannot make that many steps.")
         steps <- nrow(mm)
@@ -1360,7 +1360,7 @@ cut_at <- function(communities, no, steps) {
     return(res$membership + 1L)
   }
 
-  if (!missing(steps)) {
+  if (!is_missing(steps)) {
     if (steps > nrow(mm)) {
       cli::cli_warn("Cannot make that many steps.")
       steps <- nrow(mm)
diff --git a/R/flow.R b/R/flow.R
index ce14c85cd09..0cbac267dad 100644
--- a/R/flow.R
+++ b/R/flow.R
@@ -1107,7 +1107,7 @@ dominator_tree <- function(
   # Argument checks
   ensure_igraph(graph)
 
-  if (missing(root) || is.null(root)) {
+  if (is_missing(root) || is.null(root)) {
     cli::cli_abort("{.arg root} must be specified.")
   }
   root <- as_igraph_vs(graph, root)
diff --git a/R/indexing.R b/R/indexing.R
index 1f61e246621..aa6f7e70f26 100644
--- a/R/indexing.R
+++ b/R/indexing.R
@@ -56,14 +56,14 @@
 get_adjacency_submatrix <- function(x, i, j, attr = NULL) {
   # If i or j is NULL, assume all nodes
   # if not NULL make sure to handle duplicates correctly
-  if (missing(i)) {
+  if (is_missing(i)) {
     i_seq <- seq_len(vcount(x))
     has_i <- FALSE
   } else {
     i_seq <- i
     has_i <- TRUE
   }
-  if (missing(j)) {
+  if (is_missing(j)) {
     j_seq <- seq_len(vcount(x))
     has_j <- FALSE
   } else {
@@ -220,20 +220,20 @@ get_adjacency_submatrix <- function(x, i, j, attr = NULL) {
   ################################################################
   ## Argument checks
   if (
-    (!missing(from) || !missing(to)) &&
-      (!missing(i) || !missing(j))
+    (!is_missing(from) || !is_missing(to)) &&
+      (!is_missing(i) || !is_missing(j))
   ) {
     cli::cli_abort(
       "Cannot use {.arg from}/{.arg to} together with regular indices"
     )
   }
   if (
-    (!missing(from) && missing(to)) ||
-      (missing(from) && !missing(to))
+    (!is_missing(from) && is_missing(to)) ||
+      (is_missing(from) && !is_missing(to))
   ) {
     cli::cli_abort("Cannot use {.arg from}/{.arg to} without the other")
   }
-  if (!missing(from)) {
+  if (!is_missing(from)) {
     if ((!is.numeric(from) && !is.character(from)) || anyNA(from)) {
       cli::cli_abort(
         "{.arg from} must be a numeric or character vector without NAs"
@@ -251,7 +251,7 @@ get_adjacency_submatrix <- function(x, i, j, attr = NULL) {
 
   ##################################################################
 
-  if (!missing(from)) {
+  if (!is_missing(from)) {
     res <- get_edge_ids(x, data.frame(from, to), error = FALSE)
     if (edges) {
       ## nop
@@ -265,7 +265,7 @@ get_adjacency_submatrix <- function(x, i, j, attr = NULL) {
     return(res)
   }
 
-  if (missing(i) && missing(j)) {
+  if (is_missing(i) && is_missing(j)) {
     return(as_adjacency_matrix(
       x,
       sparse = sparse,
@@ -278,7 +278,7 @@ get_adjacency_submatrix <- function(x, i, j, attr = NULL) {
   i_has_dupes <- FALSE
   j_has_dupes <- FALSE
 
-  if (!missing(i)) {
+  if (!is_missing(i)) {
     i <- as_igraph_vs(x, i)
     if (anyDuplicated(i)) {
       i_has_dupes <- TRUE
@@ -287,7 +287,7 @@ get_adjacency_submatrix <- function(x, i, j, attr = NULL) {
       i_map <- match(i_dupl, i)
     }
   }
-  if (!missing(j)) {
+  if (!is_missing(j)) {
     j <- as_igraph_vs(x, j)
     if (anyDuplicated(j)) {
       j_has_dupes <- TRUE
@@ -382,29 +382,29 @@ get_adjacency_submatrix <- function(x, i, j, attr = NULL) {
 ) {
   getfun <- if (edges) as_adj_edge_list else as_adj_list
 
-  if (!missing(i) && !missing(from)) {
+  if (!is_missing(i) && !is_missing(from)) {
     cli::cli_abort("Cannot use both {.arg i} and {.arg from}")
   }
-  if (!missing(j) && !missing(to)) {
+  if (!is_missing(j) && !is_missing(to)) {
     cli::cli_abort("Cannot use both {.arg j} and {.arg to}")
   }
-  if (missing(i) && !missing(from)) {
+  if (is_missing(i) && !is_missing(from)) {
     i <- from
   }
-  if (missing(j) && !missing(to)) {
+  if (is_missing(j) && !is_missing(to)) {
     j <- to
   }
 
   directed_mode_in <-
-    if (missing(i) && missing(j)) {
+    if (is_missing(i) && is_missing(j)) {
       getfun(x, mode = if (directed) "out" else "all")
-    } else if (missing(j)) {
+    } else if (is_missing(j)) {
       if (!edges) {
         adjacent_vertices(x, i, mode = if (directed) "out" else "all")
       } else {
         incident_edges(x, i, mode = if (directed) "out" else "all")
       }
-    } else if (missing(i)) {
+    } else if (is_missing(i)) {
       if (!edges) {
         adjacent_vertices(x, j, mode = if (directed) "in" else "all")
       } else {
@@ -469,16 +469,16 @@ expand.grid.unordered <- function(i, j, loops = FALSE, directed = FALSE) {
   ################################################################
   ## Argument checks
   if (
-    (!missing(from) || !missing(to)) &&
-      (!missing(i) || !missing(j))
+    (!is_missing(from) || !is_missing(to)) &&
+      (!is_missing(i) || !is_missing(j))
   ) {
     cli::cli_abort(
       "Cannot use {.arg from}/{.arg to} together with regular indices"
     )
   }
   if (
-    (!missing(from) && missing(to)) ||
-      (missing(from) && !missing(to))
+    (!is_missing(from) && is_missing(to)) ||
+      (is_missing(from) && !is_missing(to))
   ) {
     cli::cli_abort("Cannot use {.arg from}/{.arg to} without the other")
   }
@@ -491,7 +491,7 @@ expand.grid.unordered <- function(i, j, loops = FALSE, directed = FALSE) {
   if (is.null(attr) && !is.null(value) && length(value) != 1) {
     cli::cli_abort("Logical or numeric value must be of length 1")
   }
-  if (!missing(from)) {
+  if (!is_missing(from)) {
     if ((!is.numeric(from) && !is.character(from)) || anyNA(from)) {
       cli::cli_abort(
         "{.arg from} must be a numeric or character vector without NAs"
@@ -509,7 +509,7 @@ expand.grid.unordered <- function(i, j, loops = FALSE, directed = FALSE) {
 
   ##################################################################
 
-  if (!missing(from)) {
+  if (!is_missing(from)) {
     if (
       is.null(value) ||
         (is.logical(value) && !value) ||
@@ -535,11 +535,11 @@ expand.grid.unordered <- function(i, j, loops = FALSE, directed = FALSE) {
       (is.null(attr) && is.numeric(value) && value == 0)
   ) {
     ## Delete edges
-    if (missing(i) && missing(j)) {
+    if (is_missing(i) && is_missing(j)) {
       todel <- seq_len(ecount(x))
-    } else if (missing(j)) {
+    } else if (is_missing(j)) {
       todel <- unlist(incident_edges(x, v = i, mode = "out"))
-    } else if (missing(i)) {
+    } else if (is_missing(i)) {
       todel <- unlist(incident_edges(x, v = j, mode = "in"))
     } else {
       edge_pairs <- expand.grid(i, j)
@@ -549,8 +549,8 @@ expand.grid.unordered <- function(i, j, loops = FALSE, directed = FALSE) {
     x <- delete_edges(x, todel)
   } else {
     ## Addition or update of an attribute (or both)
-    i <- if (missing(i)) as.numeric(V(x)) else as_igraph_vs(x, i)
-    j <- if (missing(j)) as.numeric(V(x)) else as_igraph_vs(x, j)
+    i <- if (is_missing(i)) as.numeric(V(x)) else as_igraph_vs(x, i)
+    j <- if (is_missing(j)) as.numeric(V(x)) else as_igraph_vs(x, j)
     if (length(i) != 0 && length(j) != 0) {
       edge_pairs <- expand.grid.unordered(
         i,
diff --git a/R/layout.R b/R/layout.R
index 5c028fe8959..77a98c38d80 100644
--- a/R/layout.R
+++ b/R/layout.R
@@ -635,24 +635,24 @@ component_wise <- function(merge_method = "dla") {
 normalize <- function(
   xmin = -1,
   xmax = 1,
-  ymin = NULL,
-  ymax = NULL,
-  zmin = NULL,
-  zmax = NULL
+  ymin,
+  ymax,
+  zmin,
+  zmax
 ) {
   # NULL is a legal value here (norm_coords() skips normalization along an
   # axis with a NULL limit), so the fallback to the x limits applies only
   # when an argument is not supplied at all.
-  if (missing(ymin)) {
+  if (is_missing(ymin)) {
     ymin <- xmin
   }
-  if (missing(ymax)) {
+  if (is_missing(ymax)) {
     ymax <- xmax
   }
-  if (missing(zmin)) {
+  if (is_missing(zmin)) {
     zmin <- xmin
   }
-  if (missing(zmax)) {
+  if (is_missing(zmax)) {
     zmax <- xmax
   }
 
diff --git a/R/operators.R b/R/operators.R
index 7b558ebcd61..8430b3db0ca 100644
--- a/R/operators.R
+++ b/R/operators.R
@@ -1522,7 +1522,7 @@ path <- function(...) {
 #' @method - igraph
 #' @export
 `-.igraph` <- function(e1, e2) {
-  if (missing(e2)) {
+  if (is_missing(e2)) {
     cli::cli_abort("Non-numeric argument to negation operator")
   }
   if (is_igraph(e2)) {
diff --git a/R/par.R b/R/par.R
index a57b7e8f9dc..44a5749ed25 100644
--- a/R/par.R
+++ b/R/par.R
@@ -24,11 +24,11 @@ igraph.options <- function(...) {
 #' @inheritParams igraph_opt
 #' @keywords internal
 #' @export
-getIgraphOpt <- function(x, default = NULL) {
+getIgraphOpt <- function(x, default) {
   # nocov start
   lifecycle::deprecate_warn("2.0.0", "getIgraphOpt()", "igraph_opt()")
 
-  if (missing(default)) {
+  if (is_missing(default)) {
     get_config(paste0("igraph::", x), .igraph.pars[[x]])
   } else {
     get_config(paste0("igraph::", x), default)
@@ -300,7 +300,7 @@ get_all_options <- function() {
 igraph_opt <- function(
   x,
   ...,
-  default = NULL
+  default
 ) {
   # BEGIN GENERATED ARG_HANDLE: igraph_opt, do not edit, see tools/generate-migrations.R
   # fmt: skip
@@ -337,7 +337,7 @@ igraph_opt <- function(
   }
   # END GENERATED ARG_HANDLE
 
-  if (missing(default)) {
+  if (is_missing(default)) {
     get_config(paste0("igraph::", x), .igraph.pars[[x]])
   } else {
     get_config(paste0("igraph::", x), default)
diff --git a/R/print.R b/R/print.R
index 1c2afaf9942..e76e8539c75 100644
--- a/R/print.R
+++ b/R/print.R
@@ -603,7 +603,7 @@ print.igraph <- function(
   vertex.attributes = NULL,
   edge.attributes = NULL,
   names = TRUE,
-  max.lines = NULL,
+  max.lines,
   id = NULL,
   ...
 ) {
@@ -621,7 +621,7 @@ print.igraph <- function(
   if (is.null(edge.attributes)) {
     edge.attributes <- igraph_opt("print.edge.attributes")
   }
-  if (missing(max.lines)) {
+  if (is_missing(max.lines)) {
     # NULL is a legal value here (print all lines), so the option fallback
     # applies only when the argument is not supplied at all.
     max.lines <- igraph_opt("auto.print.lines")
diff --git a/R/sparsedf.R b/R/sparsedf.R
index dfd3f78707d..5b91462423e 100644
--- a/R/sparsedf.R
+++ b/R/sparsedf.R
@@ -71,10 +71,10 @@ as.data.frame.igraphSDF <- function(x, row.names, optional, ...) {
   if (!is.character(j)) {
     cli::cli_abort("The column index must be character.")
   }
-  if (!missing(i) && !is.numeric(i)) {
+  if (!is_missing(i) && !is.numeric(i)) {
     cli::cli_abort("The row index must be numeric.")
   }
-  if (missing(i)) {
+  if (is_missing(i)) {
     rep(x[[j]], length.out = attr(x, "NROW"))
   } else {
     if (length(x[[j]]) == 1) {
@@ -91,10 +91,10 @@ as.data.frame.igraphSDF <- function(x, row.names, optional, ...) {
   if (!is.character(j)) {
     cli::cli_abort("The column index must be character.")
   }
-  if (!missing(i) && !is.numeric(i)) {
+  if (!is_missing(i) && !is.numeric(i)) {
     cli::cli_abort("Row index must be numeric, if given.")
   }
-  if (missing(i)) {
+  if (is_missing(i)) {
     if (length(value) != attr(x, "NROW") && length(value) != 1) {
       cli::cli_abort("Replacement value has the wrong length.")
     }
diff --git a/R/topology.R b/R/topology.R
index 1069c076de5..fd05c59e956 100644
--- a/R/topology.R
+++ b/R/topology.R
@@ -435,8 +435,8 @@ graph.isomorphic.bliss <- function(
   graph1,
   graph2,
   ...,
-  colors1 = NULL,
-  colors2 = NULL,
+  colors1,
+  colors2,
   sh = c("fm", "f", "fs", "fl", "flm", "fsm")
 ) {
   # BEGIN GENERATED ARG_HANDLE: graph.isomorphic.bliss, do not edit, see tools/generate-migrations.R
@@ -483,8 +483,8 @@ graph.isomorphic.bliss <- function(
   isomorphic_bliss_impl(
     graph1 = graph1,
     graph2 = graph2,
-    colors1 = if (missing(colors1)) missing_arg() else colors1,
-    colors2 = if (missing(colors2)) missing_arg() else colors2,
+    colors1 = if (is_missing(colors1)) missing_arg() else colors1,
+    colors2 = if (is_missing(colors2)) missing_arg() else colors2,
     sh = sh
   )
 }
@@ -494,10 +494,10 @@ graph.isomorphic.vf2 <- function(
   graph1,
   graph2,
   ...,
-  vertex.color1 = NULL,
-  vertex.color2 = NULL,
-  edge.color1 = NULL,
-  edge.color2 = NULL
+  vertex.color1,
+  vertex.color2,
+  edge.color1,
+  edge.color2
 ) {
   # BEGIN GENERATED ARG_HANDLE: graph.isomorphic.vf2, do not edit, see tools/generate-migrations.R
   # fmt: skip
@@ -545,18 +545,18 @@ graph.isomorphic.vf2 <- function(
   isomorphic_vf2_impl(
     graph1 = graph1,
     graph2 = graph2,
-    vertex_color1 = if (missing(vertex.color1)) {
+    vertex_color1 = if (is_missing(vertex.color1)) {
       missing_arg()
     } else {
       vertex.color1
     },
-    vertex_color2 = if (missing(vertex.color2)) {
+    vertex_color2 = if (is_missing(vertex.color2)) {
       missing_arg()
     } else {
       vertex.color2
     },
-    edge_color1 = if (missing(edge.color1)) missing_arg() else edge.color1,
-    edge_color2 = if (missing(edge.color2)) missing_arg() else edge.color2
+    edge_color1 = if (is_missing(edge.color1)) missing_arg() else edge.color1,
+    edge_color2 = if (is_missing(edge.color2)) missing_arg() else edge.color2
   )
 }
 #' @inheritParams rlang::args_dots_empty
@@ -565,10 +565,10 @@ graph.subisomorphic.vf2 <- function(
   graph1,
   graph2,
   ...,
-  vertex.color1 = NULL,
-  vertex.color2 = NULL,
-  edge.color1 = NULL,
-  edge.color2 = NULL
+  vertex.color1,
+  vertex.color2,
+  edge.color1,
+  edge.color2
 ) {
   # BEGIN GENERATED ARG_HANDLE: graph.subisomorphic.vf2, do not edit, see tools/generate-migrations.R
   # fmt: skip
@@ -616,18 +616,18 @@ graph.subisomorphic.vf2 <- function(
   subisomorphic_vf2_impl(
     graph1 = graph1,
     graph2 = graph2,
-    vertex_color1 = if (missing(vertex.color1)) {
+    vertex_color1 = if (is_missing(vertex.color1)) {
       missing_arg()
     } else {
       vertex.color1
     },
-    vertex_color2 = if (missing(vertex.color2)) {
+    vertex_color2 = if (is_missing(vertex.color2)) {
       missing_arg()
     } else {
       vertex.color2
     },
-    edge_color1 = if (missing(edge.color1)) missing_arg() else edge.color1,
-    edge_color2 = if (missing(edge.color2)) missing_arg() else edge.color2
+    edge_color1 = if (is_missing(edge.color1)) missing_arg() else edge.color1,
+    edge_color2 = if (is_missing(edge.color2)) missing_arg() else edge.color2
   )
 }
 
@@ -807,10 +807,10 @@ graph.count.isomorphisms.vf2 <- function(
   graph1,
   graph2,
   ...,
-  vertex.color1 = NULL,
-  vertex.color2 = NULL,
-  edge.color1 = NULL,
-  edge.color2 = NULL
+  vertex.color1,
+  vertex.color2,
+  edge.color1,
+  edge.color2
 ) {
   # BEGIN GENERATED ARG_HANDLE: graph.count.isomorphisms.vf2, do not edit, see tools/generate-migrations.R
   # fmt: skip
@@ -858,18 +858,18 @@ graph.count.isomorphisms.vf2 <- function(
   count_isomorphisms_vf2_impl(
     graph1 = graph1,
     graph2 = graph2,
-    vertex_color1 = if (missing(vertex.color1)) {
+    vertex_color1 = if (is_missing(vertex.color1)) {
       missing_arg()
     } else {
       vertex.color1
     },
-    vertex_color2 = if (missing(vertex.color2)) {
+    vertex_color2 = if (is_missing(vertex.color2)) {
       missing_arg()
     } else {
       vertex.color2
     },
-    edge_color1 = if (missing(edge.color1)) missing_arg() else edge.color1,
-    edge_color2 = if (missing(edge.color2)) missing_arg() else edge.color2
+    edge_color1 = if (is_missing(edge.color1)) missing_arg() else edge.color1,
+    edge_color2 = if (is_missing(edge.color2)) missing_arg() else edge.color2
   )
 }
 
@@ -958,10 +958,10 @@ graph.count.subisomorphisms.vf2 <- function(
   graph1,
   graph2,
   ...,
-  vertex.color1 = NULL,
-  vertex.color2 = NULL,
-  edge.color1 = NULL,
-  edge.color2 = NULL
+  vertex.color1,
+  vertex.color2,
+  edge.color1,
+  edge.color2
 ) {
   # BEGIN GENERATED ARG_HANDLE: graph.count.subisomorphisms.vf2, do not edit, see tools/generate-migrations.R
   # fmt: skip
@@ -1009,18 +1009,18 @@ graph.count.subisomorphisms.vf2 <- function(
   count_subisomorphisms_vf2_impl(
     graph1 = graph1,
     graph2 = graph2,
-    vertex_color1 = if (missing(vertex.color1)) {
+    vertex_color1 = if (is_missing(vertex.color1)) {
       missing_arg()
     } else {
       vertex.color1
     },
-    vertex_color2 = if (missing(vertex.color2)) {
+    vertex_color2 = if (is_missing(vertex.color2)) {
       missing_arg()
     } else {
       vertex.color2
     },
-    edge_color1 = if (missing(edge.color1)) missing_arg() else edge.color1,
-    edge_color2 = if (missing(edge.color2)) missing_arg() else edge.color2
+    edge_color1 = if (is_missing(edge.color1)) missing_arg() else edge.color1,
+    edge_color2 = if (is_missing(edge.color2)) missing_arg() else edge.color2
   )
 }
 
@@ -1267,7 +1267,7 @@ subgraph_isomorphisms <- function(
 #' isomorphism_class(g2)
 #' isomorphic(g1, g2)
 isomorphism_class <- function(graph, v) {
-  if (missing(v)) {
+  if (is_missing(v)) {
     graph.isoclass(graph)
   } else {
     graph.isoclass.subgraph(graph, v)
@@ -1457,7 +1457,7 @@ graph_from_isomorphism_class <- function(
 #' @export
 canonical_permutation <- function(
   graph,
-  colors = NULL,
+  colors,
   ...,
   sh = c("fm", "f", "fs", "fl", "flm", "fsm")
 ) {
@@ -1498,7 +1498,7 @@ canonical_permutation <- function(
 
   canonical_permutation_impl(
     graph = graph,
-    colors = if (missing(colors)) missing_arg() else colors,
+    colors = if (is_missing(colors)) missing_arg() else colors,
     sh = sh
   )
 }
@@ -1643,7 +1643,7 @@ graph.isomorphic <- function(graph1, graph2) {
 #' @export
 count_automorphisms <- function(
   graph,
-  colors = NULL,
+  colors,
   ...,
   sh = c("fm", "f", "fs", "fl", "flm", "fsm")
 ) {
@@ -1684,7 +1684,7 @@ count_automorphisms <- function(
 
   count_automorphisms_impl(
     graph = graph,
-    colors = if (missing(colors)) missing_arg() else colors,
+    colors = if (is_missing(colors)) missing_arg() else colors,
     sh = sh
   )
 }
@@ -1764,7 +1764,7 @@ count_automorphisms <- function(
 #' @export
 automorphism_group <- function(
   graph,
-  colors = NULL,
+  colors,
   ...,
   sh = c("fm", "f", "fs", "fl", "flm", "fsm"),
   details = FALSE
@@ -1808,7 +1808,7 @@ automorphism_group <- function(
 
   automorphism_group_impl(
     graph = graph,
-    colors = if (missing(colors)) missing_arg() else colors,
+    colors = if (is_missing(colors)) missing_arg() else colors,
     sh = sh,
     details = details
   )
diff --git a/R/utils-assert-args.R b/R/utils-assert-args.R
index c80e7cb9cfd..32bf688802a 100644
--- a/R/utils-assert-args.R
+++ b/R/utils-assert-args.R
@@ -47,7 +47,7 @@ igraph_match_arg <- function(
   # Materialize early, before accessing arg
   force(error_arg)
 
-  if (missing(values)) {
+  if (rlang::is_missing(values)) {
     formal.args <- formals(sys.function(sys.parent()))
     values <- eval(formal.args[[deparse(substitute(arg))]])
   }
diff --git a/R/versions.R b/R/versions.R
index ab70f20b1ac..c2d2050e626 100644
--- a/R/versions.R
+++ b/R/versions.R
@@ -50,7 +50,7 @@ pkg_graph_version <- ver_1_5_0
 #' @family versions
 #' @export
 graph_version <- function(graph) {
-  if (missing(graph)) {
+  if (is_missing(graph)) {
     return(pkg_graph_version)
   }
 
diff --git a/man/automorphism_group.Rd b/man/automorphism_group.Rd
index ad0087f2356..68966b5c57a 100644
--- a/man/automorphism_group.Rd
+++ b/man/automorphism_group.Rd
@@ -6,7 +6,7 @@
 \usage{
 automorphism_group(
   graph,
-  colors = NULL,
+  colors,
   ...,
   sh = c("fm", "f", "fs", "fl", "flm", "fsm"),
   details = FALSE
diff --git a/man/canonical_permutation.Rd b/man/canonical_permutation.Rd
index 9963a306968..63a57ced8a3 100644
--- a/man/canonical_permutation.Rd
+++ b/man/canonical_permutation.Rd
@@ -6,7 +6,7 @@
 \usage{
 canonical_permutation(
   graph,
-  colors = NULL,
+  colors,
   ...,
   sh = c("fm", "f", "fs", "fl", "flm", "fsm")
 )
diff --git a/man/count_automorphisms.Rd b/man/count_automorphisms.Rd
index 522ba3b2274..415f5188745 100644
--- a/man/count_automorphisms.Rd
+++ b/man/count_automorphisms.Rd
@@ -6,7 +6,7 @@
 \usage{
 count_automorphisms(
   graph,
-  colors = NULL,
+  colors,
   ...,
   sh = c("fm", "f", "fs", "fl", "flm", "fsm")
 )
diff --git a/man/getIgraphOpt.Rd b/man/getIgraphOpt.Rd
index 1c319890d4b..95130d24c30 100644
--- a/man/getIgraphOpt.Rd
+++ b/man/getIgraphOpt.Rd
@@ -4,7 +4,7 @@
 \alias{getIgraphOpt}
 \title{Parameters for the igraph package}
 \usage{
-getIgraphOpt(x, default = NULL)
+getIgraphOpt(x, default)
 }
 \arguments{
 \item{x}{A character string holding an option name.}
diff --git a/man/igraph_options.Rd b/man/igraph_options.Rd
index 8ba971f89fc..8ad8b04e6be 100644
--- a/man/igraph_options.Rd
+++ b/man/igraph_options.Rd
@@ -7,7 +7,7 @@
 \usage{
 igraph_options(...)
 
-igraph_opt(x, ..., default = NULL)
+igraph_opt(x, ..., default)
 }
 \arguments{
 \item{\dots}{A list may be given as the only argument, or any number of
diff --git a/man/normalize.Rd b/man/normalize.Rd
index c45f3047caf..770ada976bd 100644
--- a/man/normalize.Rd
+++ b/man/normalize.Rd
@@ -4,14 +4,7 @@
 \alias{normalize}
 \title{Normalize layout}
 \usage{
-normalize(
-  xmin = -1,
-  xmax = 1,
-  ymin = NULL,
-  ymax = NULL,
-  zmin = NULL,
-  zmax = NULL
-)
+normalize(xmin = -1, xmax = 1, ymin, ymax, zmin, zmax)
 }
 \arguments{
 \item{xmin, xmax}{Minimum and maximum for x coordinates.}
diff --git a/man/print.igraph.Rd b/man/print.igraph.Rd
index 0aa9e07f11f..5838426108c 100644
--- a/man/print.igraph.Rd
+++ b/man/print.igraph.Rd
@@ -14,7 +14,7 @@
   vertex.attributes = NULL,
   edge.attributes = NULL,
   names = TRUE,
-  max.lines = NULL,
+  max.lines,
   id = NULL,
   ...
 )