diff --git a/pkgs/applications/networking/browsers/firefox/21.0.nix b/pkgs/applications/networking/browsers/firefox/21.0.nix
index d4bec94616df..d1bcc1d718b9 100644
--- a/pkgs/applications/networking/browsers/firefox/21.0.nix
+++ b/pkgs/applications/networking/browsers/firefox/21.0.nix
@@ -41,7 +41,7 @@ rec {
       "--with-system-nspr"
       "--with-system-nss"
       # "--with-system-png" # <-- "--with-system-png won't work because the system's libpng doesn't have APNG support"
-      # "--enable-system-cairo" # <-- doesn't build
+      "--enable-system-cairo"
       "--enable-system-sqlite"
       "--disable-crashreporter"
       "--disable-tests"
@@ -72,6 +72,10 @@ rec {
 
     enableParallelBuilding = true;
 
+    patches = [
+      ./system-cairo.patch # accepted upstream, probably in 22
+    ];
+
     preConfigure =
       ''
         export NIX_LDFLAGS="$NIX_LDFLAGS -L$out/lib/xulrunner-${xulVersion}"
diff --git a/pkgs/applications/networking/browsers/firefox/system-cairo.patch b/pkgs/applications/networking/browsers/firefox/system-cairo.patch
new file mode 100644
index 000000000000..76cf4d51c9cb
--- /dev/null
+++ b/pkgs/applications/networking/browsers/firefox/system-cairo.patch
@@ -0,0 +1,73 @@
+# HG changeset patch
+# From: https://hg.mozilla.org/mozilla-central/rev/52b02042b27f
+# User Connor Behan <connor.behan@gmail.com>
+# Date 1370038985 -7200
+# Node ID 52b02042b27f75acbcb2bd4822bedb00ab680e67
+# Parent  08ed531fed70978385cf9253bbc8389b0abe76ca
+Bug 722975: Unbreak builds using --with-system-cairo. r=bas
+
+diff --git a/gfx/thebes/gfxPlatform.cpp b/gfx/thebes/gfxPlatform.cpp
+--- a/gfx/thebes/gfxPlatform.cpp
++++ b/gfx/thebes/gfxPlatform.cpp
+@@ -548,23 +548,31 @@ struct SourceSurfaceUserData
+   BackendType mBackendType;
+ };
+ 
+ void SourceBufferDestroy(void *srcSurfUD)
+ {
+   delete static_cast<SourceSurfaceUserData*>(srcSurfUD);
+ }
+ 
++#if MOZ_TREE_CAIRO
+ void SourceSnapshotDetached(cairo_surface_t *nullSurf)
+ {
+   gfxImageSurface* origSurf =
+     static_cast<gfxImageSurface*>(cairo_surface_get_user_data(nullSurf, &kSourceSurface));
+ 
+   origSurf->SetData(&kSourceSurface, NULL, NULL);
+ }
++#else
++void SourceSnapshotDetached(void *nullSurf)
++{
++  gfxImageSurface* origSurf = static_cast<gfxImageSurface*>(nullSurf);
++  origSurf->SetData(&kSourceSurface, NULL, NULL);
++}
++#endif
+ 
+ RefPtr<SourceSurface>
+ gfxPlatform::GetSourceSurfaceForSurface(DrawTarget *aTarget, gfxASurface *aSurface)
+ {
+   void *userData = aSurface->GetData(&kSourceSurface);
+ 
+   if (userData) {
+     SourceSurfaceUserData *surf = static_cast<SourceSurfaceUserData*>(userData);
+@@ -667,24 +675,28 @@ gfxPlatform::GetSourceSurfaceForSurface(
+       }
+ 
+       srcBuffer = Factory::CreateWrappingDataSourceSurface(imgSurface->Data(),
+                                                            imgSurface->Stride(),
+                                                            size, format);
+ 
+     }
+ 
++#if MOZ_TREE_CAIRO
+     cairo_surface_t *nullSurf =
+ 	cairo_null_surface_create(CAIRO_CONTENT_COLOR_ALPHA);
+     cairo_surface_set_user_data(nullSurf,
+                                 &kSourceSurface,
+                                 imgSurface,
+                                 NULL);
+     cairo_surface_attach_snapshot(imgSurface->CairoSurface(), nullSurf, SourceSnapshotDetached);
+     cairo_surface_destroy(nullSurf);
++#else
++    cairo_surface_set_mime_data(imgSurface->CairoSurface(), "mozilla/magic", (const unsigned char*) "data", 4, SourceSnapshotDetached, imgSurface.get());
++#endif
+   }
+ 
+   SourceSurfaceUserData *srcSurfUD = new SourceSurfaceUserData;
+   srcSurfUD->mBackendType = aTarget->GetType();
+   srcSurfUD->mSrcSurface = srcBuffer;
+   aSurface->SetData(&kSourceSurface, srcSurfUD, SourceBufferDestroy);
+ 
+   return srcBuffer;
+