diff --git a/wiretap/netmon.c b/wiretap/netmon.c
index 9f5d1b5578..ac5c5037d6 100644
--- a/wiretap/netmon.c
+++ b/wiretap/netmon.c
@@ -307,6 +307,15 @@ int netmon_open(wtap *wth, int *err, gchar **err_info)
 	netmon->version_major = hdr.ver_major;
 	netmon->version_minor = hdr.ver_minor;
 
+	/*
+	 * No frame table allocated yet; initialize these in case we
+	 * get an error before allocating it or when trying to allocate
+	 * it, so that the attempt to release the private data on failure
+	 * doesn't crash.
+	 */
+	netmon->frame_table_size = 0;
+	netmon->frame_table = NULL;
+
 	/*
 	 * Get the offset of the frame index table.
 	 */