diff --git a/custom_typings/minimatch-all.d.ts b/custom_typings/minimatch-all.d.ts
new file mode 100644
index 000000000..9dca100ed
--- /dev/null
+++ b/custom_typings/minimatch-all.d.ts
@@ -0,0 +1,7 @@
+declare module 'minimatch-all' {
+
+  function minimatchAll(filePath: string, globs: string[])
+      : boolean;
+
+  export = minimatchAll;
+}
diff --git a/package.json b/package.json
index 6015cefb1..fd46b5a5d 100644
--- a/package.json
+++ b/package.json
@@ -20,6 +20,7 @@
   },
   "dependencies": {
     "@types/node": "^6.0.41",
+    "minimatch-all": "^1.1.0",
     "plylog": "^0.4.0"
   },
   "devDependencies": {
diff --git a/src/index.ts b/src/index.ts
index c24ec49ba..eb3f622c6 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -11,6 +11,7 @@
 import * as fs from 'fs';
 import * as path from 'path';
 import * as logging from 'plylog';
+import minimatchAll = require('minimatch-all');
 
 const logger = logging.getLogger('polymer-project-config');
 
@@ -227,6 +228,10 @@ export class ProjectConfig {
     return (!!this.shell && (this.shell === filepath));
   }
 
+  isSource(filepath: string): boolean {
+    return minimatchAll(filepath, this.sources);
+  }
+
   /**
    * Validates that a configuration is accurate, and that all paths are
    * contained within the project root.
diff --git a/test/index_test.js b/test/index_test.js
index 1982aa738..435f80f90 100644
--- a/test/index_test.js
+++ b/test/index_test.js
@@ -238,6 +238,27 @@ suite('Project Config', () => {
 
     });
 
+    suite('isSource()', () => {
+
+      test('matches source file paths and does not match other file paths', () => {
+        const relativeRoot = 'public';
+        const absoluteRoot = path.resolve(relativeRoot);
+        const config = new ProjectConfig({
+          root: relativeRoot,
+          entrypoint: 'foo.html',
+          fragments: ['bar.html'],
+          shell: 'baz.html',
+        });
+        assert.isTrue(config.isSource(config.entrypoint));
+        assert.isTrue(config.isSource(config.shell));
+        assert.isTrue(config.isSource(path.resolve(absoluteRoot, 'foo.html')));
+        assert.isTrue(config.isSource(path.resolve(absoluteRoot, 'bar.html')));
+        assert.isTrue(config.isSource(path.resolve(absoluteRoot, 'baz.html')));
+        assert.isFalse(config.isSource(path.resolve(absoluteRoot, 'not-a-fragment.html')));
+      });
+
+    });
+
     suite('validate()', () => {
 
       test('returns true for valid configuration', () => {