diff --git a/lib/rtsp.c b/lib/rtsp.c
index 16dfa27cb5..1254c73895 100644
--- a/lib/rtsp.c
+++ b/lib/rtsp.c
@@ -706,10 +706,10 @@ CURLcode Curl_rtsp_parseheader(struct connectdata *conn,
 
     /* Find the first non-space letter */
     start = header + 9;
-    while(start && ISSPACE(*start))
+    while(*start && ISSPACE(*start))
       start++;
 
-    if(!start) {
+    if(!*start) {
       failf(data, "Got a blank Session ID");
     }
     else if(data->set.str[STRING_RTSP_SESSION_ID]) {