diff --git a/package.json b/package.json
index 26560bc4..c38b5939 100644
--- a/package.json
+++ b/package.json
@@ -33,10 +33,8 @@
         "estraverse": "^4.2.0",
         "esutils": "^2.0.2",
         "esprima": "^3.1.3",
-        "optionator": "^0.8.1"
-    },
-    "optionalDependencies": {
-        "source-map": "~0.6.1"
+        "optionator": "^0.8.1",
+        "source-map": "~0.7.2"
     },
     "devDependencies": {
         "acorn": "^4.0.4",
diff --git a/test/source-map.js b/test/source-map.js
index 8f6f2150..21e229c8 100644
--- a/test/source-map.js
+++ b/test/source-map.js
@@ -469,7 +469,7 @@ describe('source map test', function () {
         expect(result.map._names._array.length).to.be.equal(3);
     });
 
-    it('sourceContent support', function() {
+    it('sourceContent support', function(done) {
         var source = "(+ a b)"
         var ast = {
             "type": "ExpressionStatement",
@@ -499,8 +499,10 @@ describe('source map test', function () {
         expect(output.code).to.be.equal("a + b;");
 
 
-        var consumer = new sourcemap.SourceMapConsumer(output.map.toString());
-        expect(consumer.sourceContentFor("sum.ls")).to.be.equal(source);
+        new sourcemap.SourceMapConsumer(output.map.toString()).then(function(consumer) {
+          expect(consumer.sourceContentFor("sum.ls")).to.be.equal(source);
+          done();
+        });
     });
 
     it('sourceMapWithCode forces output format', function() {