--- a/gfx/thebes/gfxPrefs.h
+++ b/gfx/thebes/gfxPrefs.h
@@ -336,16 +336,17 @@ private:
   DECL_GFX_PREF(Live, "apz.x_skate_size_multiplier",           APZXSkateSizeMultiplier, float, 1.5f);
   DECL_GFX_PREF(Live, "apz.x_stationary_size_multiplier",      APZXStationarySizeMultiplier, float, 3.0f);
   DECL_GFX_PREF(Live, "apz.y_skate_highmem_adjust",            APZYSkateHighMemAdjust, float, 0.0f);
   DECL_GFX_PREF(Live, "apz.y_skate_size_multiplier",           APZYSkateSizeMultiplier, float, 2.5f);
   DECL_GFX_PREF(Live, "apz.y_stationary_size_multiplier",      APZYStationarySizeMultiplier, float, 3.5f);
   DECL_GFX_PREF(Live, "apz.zoom_animation_duration_ms",        APZZoomAnimationDuration, int32_t, 250);
   DECL_GFX_PREF(Live, "apz.scale_repaint_delay_ms",            APZScaleRepaintDelay, int32_t, 500);
 
+  DECL_GFX_PREF(Live, "browser.ui.scroll-toolbar-threshold",   ToolbarScrollThreshold, int32_t, 10);
   DECL_GFX_PREF(Live, "browser.ui.zoom.force-user-scalable",   ForceUserScalable, bool, false);
   DECL_GFX_PREF(Live, "browser.viewport.desktopWidth",         DesktopViewportWidth, int32_t, 980);
 
   DECL_GFX_PREF(Live, "dom.ipc.plugins.asyncdrawing.enabled",  PluginAsyncDrawingEnabled, bool, false);
   DECL_GFX_PREF(Live, "dom.meta-viewport.enabled",             MetaViewportEnabled, bool, false);
   DECL_GFX_PREF(Once, "dom.vr.enabled",                        VREnabled, bool, false);
   DECL_GFX_PREF(Live, "dom.vr.autoactivate.enabled",           VRAutoActivateEnabled, bool, false);
   DECL_GFX_PREF(Live, "dom.vr.navigation.timeout",             VRNavigationTimeout, int32_t, 1000);