diff --git a/src/evalfunc.c b/src/evalfunc.c
index 923a750..5b25e97 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2872,6 +2872,10 @@
     }
     if (++intidx < (int)ARRAY_LENGTH(global_functions))
     {
+	// Skip if the function doesn't have an implementation (feature not
+	// implemented).
+	if (global_functions[intidx].f_func == NULL)
+	    return (char_u *)"";
 	STRCPY(IObuff, global_functions[intidx].f_name);
 	STRCAT(IObuff, "(");
 	if (global_functions[intidx].f_max_argc == 0)