diff --git a/index.js b/index.js
index 34cc70e..5d82f2e 100644
--- a/index.js
+++ b/index.js
@@ -20,7 +20,7 @@ function readAsJSON(fileName) {
 function yamlMerge(...from) {
   const files = from.map((path) => readAsJSON(path));
 
-  const outputJSON = _.assign({}, ...files);
+  const outputJSON = _.merge({}, ...files);
   return jsYaml.dump(outputJSON);
 }
 
diff --git a/test/fixtures/merge/a.yml b/test/fixtures/merge/a.yml
new file mode 100644
index 0000000..dc12cff
--- /dev/null
+++ b/test/fixtures/merge/a.yml
@@ -0,0 +1,3 @@
+key:
+  first_value: a
+
diff --git a/test/fixtures/merge/b.yml b/test/fixtures/merge/b.yml
new file mode 100644
index 0000000..3f7708f
--- /dev/null
+++ b/test/fixtures/merge/b.yml
@@ -0,0 +1,3 @@
+key:
+  second_value: b
+
diff --git a/test/lib-test.js b/test/lib-test.js
index c74e16e..e7be997 100644
--- a/test/lib-test.js
+++ b/test/lib-test.js
@@ -31,5 +31,15 @@ describe('merge logic', function() {
         value: c
     ` + '\n');
   });
+
+  it('allows keys to trickle in from all merge sources', function () {
+    const output = merge(...fixtureFiles('merge/a.yml', 'merge/b.yml'));
+    
+    expect(output).to.equal(stripIndent`
+      key:
+        first_value: a
+        second_value: b
+    ` + '\n');
+  });
 });