diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0abd507..6c50378 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+## 0.6.0+3
+
+* Make sure to always use the canonical libraries and super declarations in
+development mode. This eliminates an uncommon issue where a single initializer
+could be ran more than once.
+
 ## 0.6.0+2
 
 * Private identifiers will now be evaluated and inlined into the bootstrap file
diff --git a/lib/src/mirror_loader.dart b/lib/src/mirror_loader.dart
index a7ac724..3865e72 100644
--- a/lib/src/mirror_loader.dart
+++ b/lib/src/mirror_loader.dart
@@ -160,9 +160,8 @@
     var annotations =
         declaration.metadata.where((m) => _filterMetadata(declaration, m));
     for (var meta in annotations) {
-      if (!_annotationsFound.containsKey(declaration)) {
-        _annotationsFound[declaration] = new Set<InstanceMirror>();
-      }
+      _annotationsFound.putIfAbsent(
+          declaration, () => new Set<InstanceMirror>());
       _annotationsFound[declaration].add(meta);
 
       // Initialize super classes first, if they are in the same library,
diff --git a/pubspec.yaml b/pubspec.yaml
index 2d0b048..a05326e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: initialize
-version: 0.6.0+2
+version: 0.6.0+3
 author: Polymer.dart Authors <web@dartlang.org>
 description: Generic building blocks for doing static initialization.
 homepage: https://github.com/dart-lang/initialize