diff --git a/ipc/msg.c b/ipc/msg.c
index e12307d..ff10d43 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -763,7 +763,10 @@
 	if (*msgtyp == 0)
 		return SEARCH_ANY;
 	if (*msgtyp < 0) {
-		*msgtyp = -*msgtyp;
+		if (*msgtyp == LONG_MIN) /* -LONG_MIN is undefined */
+			*msgtyp = LONG_MAX;
+		else
+			*msgtyp = -*msgtyp;
 		return SEARCH_LESSEQUAL;
 	}
 	if (msgflg & MSG_EXCEPT)