diff --git a/gfx/thebes/gfxPlatform.cpp b/gfx/thebes/gfxPlatform.cpp
index 594a34b23dd5..f37ec589fa8e 100644
--- a/gfx/thebes/gfxPlatform.cpp
+++ b/gfx/thebes/gfxPlatform.cpp
@@ -300,23 +300,6 @@ gfxPlatform::Init()
     sCmapDataLog = PR_NewLogModule("cmapdata");;
 #endif
 
-    bool useOffMainThreadCompositing = false;
-    useOffMainThreadCompositing = GetPrefLayersOffMainThreadCompositionEnabled() ||
-        Preferences::GetBool("browser.tabs.remote", false);
-#ifdef MOZ_X11
-    useOffMainThreadCompositing &= (PR_GetEnv("MOZ_USE_OMTC") != NULL) ||
-                                   (PR_GetEnv("MOZ_OMTC_ENABLED") != NULL);
-#endif
-
-    if (useOffMainThreadCompositing && (XRE_GetProcessType() ==
-                                        GeckoProcessType_Default)) {
-        CompositorParent::StartUp();
-        if (Preferences::GetBool("layers.async-video.enabled",false)) {
-            ImageBridgeChild::StartUp();
-        }
-
-    }
-
     /* Initialize the GfxInfo service.
      * Note: we can't call functions on GfxInfo that depend
      * on gPlatform until after it has been initialized
@@ -348,6 +331,19 @@ gfxPlatform::Init()
     mozilla::gl::GLContext::StaticInit();
 #endif
 
+    bool useOffMainThreadCompositing = GetPrefLayersOffMainThreadCompositionEnabled() ||
+        Preferences::GetBool("browser.tabs.remote", false);
+    useOffMainThreadCompositing &= GetPlatform()->SupportsOffMainThreadCompositing();
+
+    if (useOffMainThreadCompositing && (XRE_GetProcessType() ==
+                                        GeckoProcessType_Default)) {
+        CompositorParent::StartUp();
+        if (Preferences::GetBool("layers.async-video.enabled",false)) {
+            ImageBridgeChild::StartUp();
+        }
+
+    }
+
     nsresult rv;
 
 #if defined(XP_MACOSX) || defined(XP_WIN) || defined(ANDROID) // temporary, until this is implemented on others
@@ -1815,6 +1811,7 @@ gfxPlatform::GetOrientationSyncMillis() const
  */
 static bool sPrefLayersOffMainThreadCompositionEnabled = false;
 static bool sPrefLayersOffMainThreadCompositionTestingEnabled = false;
+static bool sPrefLayersOffMainThreadCompositionForceEnabled = false;
 static bool sPrefLayersAccelerationForceEnabled = false;
 static bool sPrefLayersAccelerationDisabled = false;
 static bool sPrefLayersPreferOpenGL = false;
@@ -1827,6 +1824,7 @@ void InitLayersAccelerationPrefs()
   {
     sPrefLayersOffMainThreadCompositionEnabled = Preferences::GetBool("layers.offmainthreadcomposition.enabled", false);
     sPrefLayersOffMainThreadCompositionTestingEnabled = Preferences::GetBool("layers.offmainthreadcomposition.testing.enabled", false);
+    sPrefLayersOffMainThreadCompositionForceEnabled = Preferences::GetBool("layers.offmainthreadcomposition.force-enabled", false);
     sPrefLayersAccelerationForceEnabled = Preferences::GetBool("layers.acceleration.force-enabled", false) ||
                                           Preferences::GetBool("browser.tabs.remote", false);
     sPrefLayersAccelerationDisabled = Preferences::GetBool("layers.acceleration.disabled", false);
@@ -1841,9 +1839,16 @@ bool gfxPlatform::GetPrefLayersOffMainThreadCompositionEnabled()
 {
   InitLayersAccelerationPrefs();
   return sPrefLayersOffMainThreadCompositionEnabled ||
+         sPrefLayersOffMainThreadCompositionForceEnabled ||
          sPrefLayersOffMainThreadCompositionTestingEnabled;
 }
 
+bool gfxPlatform::GetPrefLayersOffMainThreadCompositionForceEnabled()
+{
+  InitLayersAccelerationPrefs();
+  return sPrefLayersOffMainThreadCompositionForceEnabled;
+}
+
 bool gfxPlatform::GetPrefLayersAccelerationForceEnabled()
 {
   InitLayersAccelerationPrefs();
diff --git a/gfx/thebes/gfxPlatform.h b/gfx/thebes/gfxPlatform.h
index 386990fcb0b9..f01e561ff76f 100644
--- a/gfx/thebes/gfxPlatform.h
+++ b/gfx/thebes/gfxPlatform.h
@@ -462,6 +462,7 @@ public:
      * only once, and remain the same until restart.
      */
     static bool GetPrefLayersOffMainThreadCompositionEnabled();
+    static bool GetPrefLayersOffMainThreadCompositionForceEnabled();
     static bool GetPrefLayersAccelerationForceEnabled();
     static bool GetPrefLayersAccelerationDisabled();
     static bool GetPrefLayersPreferOpenGL();
@@ -629,6 +630,8 @@ private:
 
     virtual qcms_profile* GetPlatformCMSOutputProfile();
 
+    virtual bool SupportsOffMainThreadCompositing() { return true; }
+
     nsRefPtr<gfxASurface> mScreenReferenceSurface;
     nsTArray<uint32_t> mCJKPrefLangs;
     nsCOMPtr<nsIObserver> mSRGBOverrideObserver;
diff --git a/gfx/thebes/gfxPlatformGtk.cpp b/gfx/thebes/gfxPlatformGtk.cpp
index eced3d6e765c..106de1c2762f 100644
--- a/gfx/thebes/gfxPlatformGtk.cpp
+++ b/gfx/thebes/gfxPlatformGtk.cpp
@@ -9,6 +9,7 @@
 #endif
 
 #include "gfxPlatformGtk.h"
+#include "prenv.h"
 
 #include "nsUnicharUtils.h"
 #include "nsUnicodeProperties.h"
@@ -498,6 +499,17 @@ gfxPlatformGtk::GetScreenDepth() const
     return sDepth;
 }
 
+bool
+gfxPlatformGtk::SupportsOffMainThreadCompositing()
+{
+#ifdef MOZ_X11
+  return (PR_GetEnv("MOZ_USE_OMTC") != nullptr) ||
+         (PR_GetEnv("MOZ_OMTC_ENABLED") != nullptr);
+#else
+  return true;
+#endif
+}
+
 qcms_profile *
 gfxPlatformGtk::GetPlatformCMSOutputProfile()
 {
diff --git a/gfx/thebes/gfxPlatformGtk.h b/gfx/thebes/gfxPlatformGtk.h
index a536c934a84e..57591511d349 100644
--- a/gfx/thebes/gfxPlatformGtk.h
+++ b/gfx/thebes/gfxPlatformGtk.h
@@ -130,6 +130,8 @@ protected:
 
 private:
     virtual qcms_profile *GetPlatformCMSOutputProfile();
+
+    virtual bool SupportsOffMainThreadCompositing();
 #ifdef MOZ_X11
     static bool sUseXRender;
 #endif
diff --git a/gfx/thebes/gfxPlatformMac.cpp b/gfx/thebes/gfxPlatformMac.cpp
index b482129deb84..12375d21f4da 100644
--- a/gfx/thebes/gfxPlatformMac.cpp
+++ b/gfx/thebes/gfxPlatformMac.cpp
@@ -431,6 +431,17 @@ gfxPlatformMac::UseAcceleratedCanvas()
   return OSXVersion() >= 0x1070 && Preferences::GetBool("gfx.canvas.azure.accelerated", false);
 }
 
+bool
+gfxPlatformMac::SupportsOffMainThreadCompositing()
+{
+  // 10.6.X has crashes on tinderbox with OMTC, so disable it
+  // for now.
+  if (OSXVersion() >= 0x1070) {
+    return true;
+  }
+  return GetPrefLayersOffMainThreadCompositionForceEnabled();
+}
+
 qcms_profile *
 gfxPlatformMac::GetPlatformCMSOutputProfile()
 {
diff --git a/gfx/thebes/gfxPlatformMac.h b/gfx/thebes/gfxPlatformMac.h
index ebf961d80bd7..a9e34abb4f46 100644
--- a/gfx/thebes/gfxPlatformMac.h
+++ b/gfx/thebes/gfxPlatformMac.h
@@ -89,6 +89,8 @@ public:
 private:
     virtual qcms_profile* GetPlatformCMSOutputProfile();
 
+    virtual bool SupportsOffMainThreadCompositing();
+
     // read in the pref value for the lower threshold on font anti-aliasing
     static uint32_t ReadAntiAliasingThreshold();
 
diff --git a/modules/libpref/src/init/all.js b/modules/libpref/src/init/all.js
index 77ae3124e3f5..15074ad058ee 100644
--- a/modules/libpref/src/init/all.js
+++ b/modules/libpref/src/init/all.js
@@ -4015,7 +4015,11 @@ pref("layers.acceleration.draw-fps", false);
 
 pref("layers.draw-borders", false);
 
+#ifdef XP_MACOSX
+pref("layers.offmainthreadcomposition.enabled", true);
+#else
 pref("layers.offmainthreadcomposition.enabled", false);
+#endif
 // same effect as layers.offmainthreadcomposition.enabled, but specifically for
 // use with tests.
 pref("layers.offmainthreadcomposition.testing.enabled", false);