diff --git a/lib/sprockets/manifest.rb b/lib/sprockets/manifest.rb
index 9e6329e00..2d42c9f8b 100644
--- a/lib/sprockets/manifest.rb
+++ b/lib/sprockets/manifest.rb
@@ -161,7 +161,8 @@ def find_sources(*args)
         end
       else
         args.each do |path|
-          yield File.binread(File.join(dir, assets[path]))
+          asset = assets[path]
+          yield File.binread(File.join(dir, asset)) if asset
         end
       end
     end
diff --git a/test/test_manifest.rb b/test/test_manifest.rb
index 323bb3229..acef521ea 100644
--- a/test/test_manifest.rb
+++ b/test/test_manifest.rb
@@ -634,7 +634,13 @@ def teardown
     manifest = Sprockets::Manifest.new(@env, @dir)
 
     result = manifest.find_sources("mobile/a.js", "mobile/b.js")
-    assert_equal ["var A;\n", "var B;\n"], result.to_a
+    assert_equal ["var A;\n", "var B;\n"], result.to_a.sort
+
+    result = manifest.find_sources("not_existent.js", "also_not_existent.js")
+    assert_equal [], result.to_a
+
+    result = manifest.find_sources("mobile/a.js", "also_not_existent.js")
+    assert_equal ["var A;\n"], result.to_a
   end
 
   test "find_sources without environment" do
@@ -645,6 +651,12 @@ def teardown
 
     result = manifest.find_sources("mobile/a.js", "mobile/b.js")
     assert_equal ["var A;\n", "var B;\n"], result.to_a
+
+    result = manifest.find_sources("not_existent.js", "also_not_existent.js")
+    assert_equal [], result.to_a
+
+    result = manifest.find_sources("mobile/a.js", "also_not_existent.js")
+    assert_equal ["var A;\n"], result.to_a
   end
 
   test "compress non-binary assets" do