diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index 3ccf34fc1c53..64bc440b1181 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -423,7 +423,7 @@ static const char *sip_skip_whitespace(const char *dptr, const char *limit)
 		dptr = sip_follow_continuation(dptr, limit);
 		break;
 	}
-	return dptr;
+	return dptr < limit ? dptr : NULL;
 }
 
 /* Search within a SIP header value, dealing with continuation lines */