diff --git a/docs/reference/gio/overview.xml b/docs/reference/gio/overview.xml
index dcb1bdb73..a72bcc6c6 100644
--- a/docs/reference/gio/overview.xml
+++ b/docs/reference/gio/overview.xml
@@ -362,13 +362,23 @@ Gvfs is also heavily distributed and relies on a session bus to be present.
       </para>
     </formalpara>
 
+    <formalpara>
+      <title><envar>GIO_MODULE_DIR</envar></title>
+
+      <para>
+        When this environment variable is set to a path, GIO will load
+	modules from this alternate directory instead of the directory
+	built into GIO. This is useful when running tests, for example.
+      </para>
+    </formalpara>
+
     <formalpara>
       <title><envar>GIO_EXTRA_MODULES</envar></title>
 
       <para>
         When this environment variable is set to a path, or a set of
         paths separated by a colon, GIO will attempt to load
-        modules from within the path.
+        additional modules from within the path.
       </para>
     </formalpara>
 
diff --git a/gio/giomodule.c b/gio/giomodule.c
index 17d55de6e..24986598e 100644
--- a/gio/giomodule.c
+++ b/gio/giomodule.c
@@ -1017,6 +1017,7 @@ _g_io_modules_ensure_loaded (void)
   static gboolean loaded_dirs = FALSE;
   const char *module_path;
   GIOModuleScope *scope;
+  const gchar *module_dir;
 
   _g_io_modules_ensure_extension_points_registered ();
   
@@ -1045,7 +1046,11 @@ _g_io_modules_ensure_loaded (void)
 	}
 
       /* Then load the compiled in path */
-      g_io_modules_scan_all_in_directory_with_scope (GIO_MODULE_DIR, scope);
+      module_dir = g_getenv ("GIO_MODULE_DIR");
+      if (module_dir == NULL)
+        module_dir = GIO_MODULE_DIR;
+
+      g_io_modules_scan_all_in_directory_with_scope (module_dir, scope);
 
       g_io_module_scope_free (scope);