diff --git a/src/vim9compile.c b/src/vim9compile.c
index c3c3808..07aacb3 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -7142,6 +7142,10 @@
 
 	    // TODO: other commands with an expression argument
 
+	    case CMD_SIZE:
+		    semsg(_("E476: Invalid command: %s"), ea.cmd);
+		    goto erret;
+
 	    default:
 		    // Not recognized, execute with do_cmdline_cmd().
 		    ea.arg = p;