diff --git a/sdk/.gitignore b/sdk/.gitignore
index dfb3fdda641..c04bbfa9dc9 100644
--- a/sdk/.gitignore
+++ b/sdk/.gitignore
@@ -1,4 +1,5 @@
+.idea
+.pub/
+lib/_sdkext
 packages
 pubspec.lock
-.pub/
-.idea
diff --git a/sdk/BUILD.gn b/sdk/BUILD.gn
index ba792c796ba..cd38020c4cd 100644
--- a/sdk/BUILD.gn
+++ b/sdk/BUILD.gn
@@ -8,7 +8,6 @@ dart_pkg("sky") {
   sources = [
     "CHANGELOG.md",
     "bin/init.dart",
-    "lib/_sdkext",
     "lib/animation/animation_performance.dart",
     "lib/animation/curves.dart",
     "lib/animation/fling_curve.dart",
@@ -113,6 +112,11 @@ dart_pkg("sky") {
     "//sky/engine/bindings/sky_internals.dart",
     "//sky/engine/bindings/builtin_natives.dart",
   ]
+  sdk_ext_mappings = [
+    "dart:sky,dart_sky.dart",
+    "dart:sky.internals,sky_internals.dart",
+    "dart:sky_builtin_natvies,builtin_natives.dart",
+  ]
 }
 
 action("material_design_icons") {
diff --git a/sdk/lib/_sdkext b/sdk/lib/_sdkext
deleted file mode 100644
index 3f60def4d15..00000000000
--- a/sdk/lib/_sdkext
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "dart:sky": "../sdk_ext/dart_sky.dart",
-  "dart:sky.internals": "../sdk_ext/sky_internals.dart",
-  "dart:sky_builtin_natvies": "../sdk_ext/builtin_natives.dart"
-}