diff --git a/src/e1cap_dump.c b/src/e1cap_dump.c
index 027aa82..c172b55 100644
--- a/src/e1cap_dump.c
+++ b/src/e1cap_dump.c
@@ -78,7 +78,7 @@
 static void handle_hdlc_frame_content(const uint8_t *data, unsigned int len,
 				      void *priv)
 {
-	if (g_pcap_fd && len >= 4) {
+	if (g_pcap_fd >= 0 && len >= 4) {
 		uint8_t *cur = msgb_put(g_pcap_msg, len-2);
 		memcpy(cur, data, len-2);
 		printf("==> %s\n", msgb_hexdump(g_pcap_msg));