diff --git a/lib/pubcache.dart b/lib/pubcache.dart
index a11da69..e9516ce 100644
--- a/lib/pubcache.dart
+++ b/lib/pubcache.dart
@@ -97,18 +97,18 @@
   String get name => path.basename(_dir.path);
 
   Version get version {
-    if (_packageRefs == null) _parsePubspec();
+    if (_packageRefs == null) _parsePubspecLock();
     return _version;
   }
 
   List<PackageRef> getPackageRefs() {
-    if (_packageRefs == null) _parsePubspec();
+    if (_packageRefs == null) _parsePubspecLock();
     return _packageRefs;
   }
 
   String toString() => '${name} ${version}';
 
-  void _parsePubspec() {
+  void _parsePubspecLock() {
     File pubspecLock = new File(path.join(_dir.path, 'pubspec.lock'));
     Map doc = yaml.loadYaml(pubspecLock.readAsStringSync());
     Map packages = doc['packages'];
diff --git a/pubspec.yaml b/pubspec.yaml
index 7a8be58..6a3a6a0 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -8,9 +8,9 @@
   sdk: '>=1.0.0 <2.0.0'
 
 dependencies:
-  path: any
-  pub_semver: any
-  yaml: any
+  path: '^1.0.0'
+  pub_semver: '^1.0.0'
+  yaml: '^2.0.0'
 
 dev_dependencies:
   unittest: any