diff --git a/src/nvim/eval/userfunc.c b/src/nvim/eval/userfunc.c
index f0c57eee40..3f9f94b5df 100644
--- a/src/nvim/eval/userfunc.c
+++ b/src/nvim/eval/userfunc.c
@@ -2500,19 +2500,14 @@ static int get_function_body(exarg_T *eap, garray_T *newlines, char *line_arg_in
       }
 
       // Check for ":append", ":change", ":insert".
-      p = skip_range(p, NULL);
-      if ((p[0] == 'a' && (!ASCII_ISALPHA(p[1]) || p[1] == 'p'))
-          || (p[0] == 'c'
-              && (!ASCII_ISALPHA(p[1])
-                  || (p[1] == 'h' && (!ASCII_ISALPHA(p[2])
-                                      || (p[2] == 'a'
-                                          && (strncmp(&p[3], "nge", 3) != 0
-                                              || !ASCII_ISALPHA(p[6])))))))
-          || (p[0] == 'i'
-              && (!ASCII_ISALPHA(p[1]) || (p[1] == 'n'
-                                           && (!ASCII_ISALPHA(p[2])
-                                               || (p[2] == 's')))))) {
+      char *const tp = p = skip_range(p, NULL);
+      if ((checkforcmd(&p, "append", 1)
+           || checkforcmd(&p, "change", 1)
+           || checkforcmd(&p, "insert", 1))
+          && (*p == '!' || *p == '|' || ascii_iswhite_nl_or_nul(*p))) {
         skip_until = xmemdupz(".", 1);
+      } else {
+        p = tp;
       }
 
       // heredoc: Check for ":python <<EOF", ":lua <<EOF", etc.
diff --git a/test/old/testdir/test_vimscript.vim b/test/old/testdir/test_vimscript.vim
index 7f29c7f651..2838fd1fc2 100644
--- a/test/old/testdir/test_vimscript.vim
+++ b/test/old/testdir/test_vimscript.vim
@@ -6813,6 +6813,52 @@ func Test_script_lines()
     catch
 	call assert_exception('Vim(function):E1145: Missing heredoc end marker: .')
     endtry
+
+    " More test for :append, :change, :insert
+    let cmds = ["append", "change", "insert"]
+    let suffixes = ["", "!", "|", "|xyz", " "]
+
+    for c in cmds
+      " Single character (with some accepted trailing characters)
+      for s in suffixes
+        let cmd = c[:0] .. s
+        let line = ["func LinesCheck()", cmd, "", "endfunc", "call LinesCheck()"]
+        call writefile(line, 'Xfunc', 'D')
+        call assert_fails('source Xfunc', 'E1145: Missing heredoc end marker: .', $'"{cmd}"')
+      endfor
+
+      " Unnecessary arguments
+      let cmd = c[:2] .. " end"
+      let line[1] = cmd
+      call writefile(line, 'Xfunc', 'D')
+      call assert_fails('source Xfunc', 'E488: Trailing characters: end:', $'"{cmd}"')
+
+      " Extra characters at the end (i.e., other commands)
+      let cmd = c .. "x"
+      let line[1] = cmd
+      call writefile(line, 'Xfunc', 'D')
+      call assert_fails('source Xfunc', 'E492: Not an editor command:', $'"{cmd}"')
+    endfor
+
+    let line =<< trim END
+    func AppendCheck()
+      apple
+    endfunc
+    call AppendCheck()
+    END
+    call writefile(line, 'Xfunc', 'D')
+    call assert_fails('source Xfunc', 'E492: Not an editor command:   apple')
+
+    let line =<< trim END
+    func AppendCheck()
+      command! apple :echo "hello apple"
+      apple
+    endfunc
+    call AppendCheck()
+    END
+    call writefile(line, 'Xfunc', 'D')
+    call assert_fails('source Xfunc', 'E183: User defined commands must start with an uppercase letter')
+
 endfunc
 
 "-------------------------------------------------------------------------------