diff --git a/glib/gfileutils.c b/glib/gfileutils.c
index dbbd12011..8681b1326 100644
--- a/glib/gfileutils.c
+++ b/glib/gfileutils.c
@@ -2754,8 +2754,12 @@ g_canonicalize_filename (const gchar *filename,
     *output = G_DIR_SEPARATOR;
 
   /* 1 to re-increment after the final decrement above (so that output >= canon),
-   * and 1 to skip the first `/` */
-  output += 2;
+   * and 1 to skip the first `/`. There might not be a first `/` if
+   * the @canon is a Windows `//server/share` style path with no
+   * trailing directories. @after_root will be '\0' in that case. */
+  output++;
+  if (*output == G_DIR_SEPARATOR)
+    output++;
 
   /* POSIX allows double slashes at the start to mean something special
    * (as does windows too). So, "//" != "/", but more than two slashes