diff --git a/gio/gosxappinfo.h b/gio/gosxappinfo.h
index 7beeaad16..793ce1fcd 100644
--- a/gio/gosxappinfo.h
+++ b/gio/gosxappinfo.h
@@ -43,7 +43,7 @@ GLIB_AVAILABLE_IN_2_52
 GType   g_osx_app_info_get_type           (void) G_GNUC_CONST;
 
 GLIB_AVAILABLE_IN_2_52
-char  * g_osx_app_info_get_filename       (GOsxAppInfo *info);
+const char *g_osx_app_info_get_filename   (GOsxAppInfo *info);
 
 GLIB_AVAILABLE_IN_2_52
 GList * g_osx_app_info_get_all_for_scheme (const gchar *scheme);
diff --git a/gio/gosxappinfo.m b/gio/gosxappinfo.m
index 849d63575..03c373778 100644
--- a/gio/gosxappinfo.m
+++ b/gio/gosxappinfo.m
@@ -168,6 +168,7 @@ get_bundle_string_value (NSBundle *bundle,
 static CFStringRef
 create_cfstring_from_cstr (const gchar *cstr)
 {
+  g_return_val_if_fail (cstr != NULL, NULL);
   return CFStringCreateWithCString (NULL, cstr, kCFStringEncodingUTF8);
 }
 
@@ -226,8 +227,8 @@ url_escape_hostname (const char *url)
 }
 
 static CFURLRef
-create_url_from_cstr (gchar    *cstr,
-                      gboolean  is_file)
+create_url_from_cstr (const gchar *cstr,
+                      gboolean     is_file)
 {
   gchar *puny_cstr;
   CFStringRef str;
@@ -279,11 +280,17 @@ create_urlspec_for_appinfo (GOsxAppInfo *info,
                             GList            *uris,
                             gboolean          are_files)
 {
-  LSLaunchURLSpec *urlspec = g_new0 (LSLaunchURLSpec, 1);
-  gchar *app_cstr = g_osx_app_info_get_filename (info);
+  LSLaunchURLSpec *urlspec = NULL;
+  const gchar *app_cstr;
+
+  g_return_val_if_fail (G_IS_OSX_APP_INFO (info), NULL);
+
+  urlspec = g_new0 (LSLaunchURLSpec, 1);
+  app_cstr = g_osx_app_info_get_filename (info);
+  g_assert (app_cstr != NULL);
 
   /* Strip file:// from app url but ensure filesystem url */
-  urlspec->appURL = create_url_from_cstr (app_cstr + 7, TRUE);
+  urlspec->appURL = create_url_from_cstr (app_cstr + strlen ("file://"), TRUE);
   urlspec->launchFlags = kLSLaunchDefaults;
   urlspec->itemURLs = create_url_list_from_glist (uris, are_files);
 
@@ -402,7 +409,7 @@ g_osx_app_info_get_executable (GAppInfo *appinfo)
   return info->executable;
 }
 
-char *
+const char *
 g_osx_app_info_get_filename (GOsxAppInfo *info)
 {
   g_return_val_if_fail (info != NULL, NULL);
@@ -431,7 +438,8 @@ g_osx_app_info_get_icon (GAppInfo *appinfo)
 
   if (!info->icon)
     {
-      gchar *icon_name, *app_uri, *icon_uri;
+      const gchar *app_uri;
+      gchar *icon_name, *icon_uri;
       GFile *file;
 
       icon_name = get_bundle_string_value (info->bundle, @"CFBundleIconFile");
@@ -439,7 +447,7 @@ g_osx_app_info_get_icon (GAppInfo *appinfo)
         return NULL;
 
       app_uri = g_osx_app_info_get_filename (info);
-      icon_uri = g_strconcat (app_uri + 7, "/Contents/Resources/", icon_name,
+      icon_uri = g_strconcat (app_uri + strlen ("file://"), "/Contents/Resources/", icon_name,
                               g_str_has_suffix (icon_name, ".icns") ? NULL : ".icns", NULL);
       g_free (icon_name);
 
@@ -459,9 +467,14 @@ g_osx_app_info_launch_internal (GAppInfo  *appinfo,
                                      GError   **error)
 {
   GOsxAppInfo *info = G_OSX_APP_INFO (appinfo);
-  LSLaunchURLSpec *urlspec = create_urlspec_for_appinfo (info, uris, are_files);
+  LSLaunchURLSpec *urlspec;
   gint ret, success = TRUE;
 
+  g_return_val_if_fail (G_IS_OSX_APP_INFO (appinfo), FALSE);
+  g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
+
+  urlspec = create_urlspec_for_appinfo (info, uris, are_files);
+
   if ((ret = LSOpenFromURLSpec (urlspec, NULL)))
     {
       /* TODO: Better error codes */