diff --git a/gfx/cairo/cairo/src/cairo-xlib-display.c b/gfx/cairo/cairo/src/cairo-xlib-display.c
--- a/gfx/cairo/cairo/src/cairo-xlib-display.c
+++ b/gfx/cairo/cairo/src/cairo-xlib-display.c
@@ -216,6 +216,8 @@ _cairo_xlib_display_get (Display *dpy)
     XExtCodes *codes;
     int major_unused, minor_unused;
 
+    static int buggy_repeat_force = -1;
+
     /* There is an apparent deadlock between this mutex and the
      * mutex for the display, but it's actually safe. For the
      * app to call XCloseDisplay() while any other thread is
@@ -308,6 +310,26 @@ _cairo_xlib_display_get (Display *dpy)
 	if (VendorRelease (dpy) <= 40500000)
 	    display->buggy_repeat = TRUE;
     }
+
+    /* XXX workaround; see https://bugzilla.mozilla.org/show_bug.cgi?id=413583 */
+    /* If buggy_repeat_force == -1, then initialize.
+     *    - set to -2, meaning "nothing was specified", and we trust the above detection.
+     *    - if MOZ_CAIRO_BUGGY_REPEAT is '0' (exactly), then force buggy repeat off
+     *    - if MOZ_CAIRO_BUGGY_REPEAT is '1' (exactly), then force buggy repeat on
+     */
+    if (buggy_repeat_force == -1) {
+        const char *flag = getenv("MOZ_CAIRO_FORCE_BUGGY_REPEAT");
+
+        buggy_repeat_force = -2;
+
+        if (flag && flag[0] == '0')
+            buggy_repeat_force = 0;
+        else if (flag && flag[0] == '1')
+            buggy_repeat_force = 1;
+    }
+
+    if (buggy_repeat_force != -2)
+        display->buggy_repeat = (buggy_repeat_force == 1);
 
     display->next = _cairo_xlib_display_list;
     _cairo_xlib_display_list = display;