diff --git a/mongoose.c b/mongoose.c
index 900fd175..4188d24a 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -2787,8 +2787,8 @@ void mg_http_serve_file(struct mg_connection *c, struct mg_http_message *hm,
   // Failed to open, and page404 is configured? Open it, then
   if (fd == NULL && opts->page404 != NULL) {
     fd = mg_fs_open(fs, opts->page404, MG_FS_READ);
-    mime = guess_content_type(mg_str(path), opts->mime_types);
     path = opts->page404;
+    mime = guess_content_type(mg_str(path), opts->mime_types);
   }
 
   if (fd == NULL || fs->st(path, &size, &mtime) == 0) {
diff --git a/src/http.c b/src/http.c
index ff76dfbf..680ec051 100644
--- a/src/http.c
+++ b/src/http.c
@@ -571,8 +571,8 @@ void mg_http_serve_file(struct mg_connection *c, struct mg_http_message *hm,
   // Failed to open, and page404 is configured? Open it, then
   if (fd == NULL && opts->page404 != NULL) {
     fd = mg_fs_open(fs, opts->page404, MG_FS_READ);
-    mime = guess_content_type(mg_str(path), opts->mime_types);
     path = opts->page404;
+    mime = guess_content_type(mg_str(path), opts->mime_types);
   }
 
   if (fd == NULL || fs->st(path, &size, &mtime) == 0) {