diff --git a/engine.c b/engine.c
--- a/engine.c
+++ b/engine.c
@@ -887,7 +887,7 @@ int32 CmdRenameEngine(int x, int y, uint
 {
 	StringID str;
 
-	if (!IsEngineIndex(p1)) return CMD_ERROR;
+	if (!IsEngineIndex(p1) || _cmd_text[0] == '\0') return CMD_ERROR;
 
 	str = AllocateNameUnique(_cmd_text, 0);
 	if (str == 0) return CMD_ERROR;