diff --git a/src/option.c b/src/option.c
index 53e956c..180aca2 100644
--- a/src/option.c
+++ b/src/option.c
@@ -4393,6 +4393,21 @@
 }
 
 /*
+ * Process the new 'wildchar' / 'wildcharm' option value.
+ */
+    char *
+did_set_wildchar(optset_T *args)
+{
+    long c = *(long *)args->os_varp;
+
+    // Don't allow key values that wouldn't work as wildchar.
+    if (c == Ctrl_C || c == '\n' || c == '\r' || c == K_KENTER)
+	return e_invalid_argument;
+
+    return NULL;
+}
+
+/*
  * Process the new 'window' option value.
  */
     char *