diff --git a/ai/ai.c b/ai/ai.c
index 759a764f48..60cb8c785b 100644
--- a/ai/ai.c
+++ b/ai/ai.c
@@ -137,7 +137,7 @@ int32 AI_DoCommandChecked(uint tile, uint32 p1, uint32 p2, uint32 flags, uint pr
 
 	res = AI_DoCommand(tile, p1, p2, flags & ~DC_EXEC, procc);
 	if (CmdFailed(res))
-		return -1;
+		return CMD_ERROR;
 
 	/* Save the command and his things, together with the unique_id */
 	new = malloc(sizeof(AICommand));