diff --git a/gfx/thebes/gfxPrefs.h b/gfx/thebes/gfxPrefs.h
index 2319074128e7..c9020cfa7d81 100644
--- a/gfx/thebes/gfxPrefs.h
+++ b/gfx/thebes/gfxPrefs.h
@@ -343,7 +343,7 @@ private:
   DECL_GFX_PREF(Live, "layout.css.scroll-snap.prediction-sensitivity", ScrollSnapPredictionSensitivity, float, 0.750f);
   DECL_GFX_PREF(Once, "layout.css.touch_action.enabled",       TouchActionEnabled, bool, false);
   DECL_GFX_PREF(Live, "layout.display-list.dump",              LayoutDumpDisplayList, bool, false);
-  DECL_GFX_PREF(Live, "layout.event-regions.enabled",          LayoutEventRegionsEnabled, bool, false);
+  DECL_GFX_PREF(Live, "layout.event-regions.enabled",          LayoutEventRegionsEnabledDoNotUseDirectly, bool, false);
   DECL_GFX_PREF(Once, "layout.frame_rate",                     LayoutFrameRate, int32_t, -1);
   DECL_GFX_PREF(Once, "layout.paint_rects_separately",         LayoutPaintRectsSeparately, bool, true);
 
diff --git a/layout/base/nsDisplayList.h b/layout/base/nsDisplayList.h
index 25b5e61d2cd9..2046ccbb7757 100644
--- a/layout/base/nsDisplayList.h
+++ b/layout/base/nsDisplayList.h
@@ -347,7 +347,9 @@ public:
   bool IsBuildingLayerEventRegions()
   {
     if (mMode == PAINTING) {
-      return (gfxPrefs::LayoutEventRegionsEnabled() ||
+      // Note: this is the only place that gets to query LayoutEventRegionsEnabled
+      // 'directly' - other code should call this function.
+      return (gfxPrefs::LayoutEventRegionsEnabledDoNotUseDirectly() ||
               gfxPrefs::AsyncPanZoomEnabled());
     }
     return false;