diff --git a/libavformat/avio.c b/libavformat/avio.c
index b00cc9d349..f6af0cb9e6 100644
--- a/libavformat/avio.c
+++ b/libavformat/avio.c
@@ -220,7 +220,9 @@ int ffurl_alloc(URLContext **puc, const char *filename, int flags,
                                      "Missing call to av_register_all()?\n");
     }
 
-    if (filename[proto_len] != ':' &&  filename[proto_len] != ',' || is_dos_path(filename))
+    if (filename[proto_len] != ':' &&
+        (filename[proto_len] != ',' || !strchr(filename + proto_len + 1, ':')) ||
+        is_dos_path(filename))
         strcpy(proto_str, "file");
     else
         av_strlcpy(proto_str, filename, FFMIN(proto_len+1, sizeof(proto_str)));