diff --git a/include/osmocom/core/msgb.h b/include/osmocom/core/msgb.h
index 9c99cad..b057caa 100644
--- a/include/osmocom/core/msgb.h
+++ b/include/osmocom/core/msgb.h
@@ -373,6 +373,8 @@
  */
 static inline int msgb_trim(struct msgb *msg, int len)
 {
+	if (len < 0)
+		MSGB_ABORT(msg, "Negative length is not allowed\n");
 	if (len > msg->data_len)
 		return -1;