diff --git a/src/bits.c b/src/bits.c
index 4c67bdd..a159fc9 100644
--- a/src/bits.c
+++ b/src/bits.c
@@ -173,7 +173,7 @@
 			return;
 	}
 
-	for (i = unaligned_cnt; i < len; i += 4) {
+	for (i = unaligned_cnt; i + 3 < len; i += 4) {
 		uint32_t *cur = (uint32_t *) (buf + i);
 		*cur = osmo_revbytebits_32(*cur);
 		len_remain -= 4;