diff --git a/index.js b/index.js
index d59a7f2..e2e23be 100644
--- a/index.js
+++ b/index.js
@@ -17,6 +17,8 @@ module.exports = UglifyWriter;
 UglifyWriter.prototype = Object.create(Plugin.prototype);
 UglifyWriter.prototype.constructor = UglifyWriter;
 
+const silent = process.argv.indexOf('--silent') !== -1;
+
 function UglifyWriter (inputNodes, options) {
   if (!(this instanceof UglifyWriter)) {
     return new UglifyWriter(inputNodes, options);
@@ -98,7 +100,12 @@ UglifyWriter.prototype.processFile = function(inFile, outFile, relativePath, out
 
     if (srcURL.existsIn(src)) {
       let url = srcURL.getFrom(src);
-      sourceMap.content = JSON.parse(fs.readFileSync(path.join(path.dirname(inFile), url)));
+      let sourceMapPath = path.join(path.dirname(inFile), url);
+      if (fs.existsSync(sourceMapPath)) {
+        sourceMap.content = JSON.parse(fs.readFileSync(sourceMapPath));
+      } else if (!silent) {
+        console.warn(`[WARN] (broccoli-uglify-sourcemap) "${url}" referenced in "${relativePath}" could not be found`);
+      }
     }
 
     options = defaults(options, { sourceMap });
@@ -111,7 +118,7 @@ UglifyWriter.prototype.processFile = function(inFile, outFile, relativePath, out
   var total = end - start;
   debug('[finished]: %s %dKB in %dms', relativePath, (result.code.length / 1000), total);
 
-  if (total > 20000 && process.argv.indexOf('--silent') === -1) {
+  if (total > 20000 && !silent) {
     console.warn('[WARN] (broccoli-uglify-sourcemap) Minifying: `' + relativePath + '` took: ' + total + 'ms (more than 20,000ms)');
   }
 
diff --git a/test/__snapshots__/test.js.snap b/test/__snapshots__/test.js.snap
index ce7ce45..68a1451 100644
--- a/test/__snapshots__/test.js.snap
+++ b/test/__snapshots__/test.js.snap
@@ -9,6 +9,7 @@ Object {
   "something.css": "#id {
     background: white;
 }",
+  "with-broken-sourcemap.js": "function meaningOfLife(){throw new Error(42)}",
 }
 `;
 
@@ -45,6 +46,9 @@ function third(){
   "something.css": "#id {
     background: white;
 }",
+  "with-broken-sourcemap.js": "function meaningOfLife(){throw new Error(42)}
+//# sourceMappingURL=with-broken-sourcemap.map",
+  "with-broken-sourcemap.map": "{\\"version\\":3,\\"sources\\":[\\"0\\"],\\"names\\":[\\"meaningOfLife\\",\\"Error\\"],\\"mappings\\":\\"AAAA,SAASA,gBAEP,MAAM,IAAIC,MADa\\",\\"file\\":\\"with-broken-sourcemap.js\\"}",
 }
 `;
 
@@ -69,6 +73,9 @@ Object {
   "something.css": "#id {
     background: white;
 }",
+  "with-broken-sourcemap.js": "function meaningOfLife(){throw new Error(42)}
+//# sourceMappingURL=with-broken-sourcemap.map",
+  "with-broken-sourcemap.map": "{\\"version\\":3,\\"sources\\":[\\"0\\"],\\"names\\":[\\"meaningOfLife\\",\\"Error\\"],\\"mappings\\":\\"AAAA,SAASA,gBAEP,MAAM,IAAIC,MADa\\",\\"file\\":\\"with-broken-sourcemap.js\\"}",
 }
 `;
 
@@ -80,6 +87,7 @@ Object {
   },
   "maps": Object {
     "no-upstream-sourcemap.map": "{\\"version\\":3,\\"sources\\":[\\"0\\"],\\"names\\":[\\"meaningOfLife\\",\\"Error\\",\\"boom\\",\\"somethingElse\\",\\"fourth\\",\\"third\\"],\\"mappings\\":\\"AACA,SAASA,gBAEP,MAAM,IAAIC,MADa,IAIzB,SAASC,OACP,MAAM,IAAID,MAAM,QAGlB,SAASE,gBACP,MAAM,IAAIF,MAAM,kBAMlB,SAASG,SACP,MAAM,IAAIH,MAAM,UAGlB,SAASI,QACP,MAAM,IAAIJ,MAAM\\",\\"file\\":\\"no-upstream-sourcemap.js\\"}",
+    "with-broken-sourcemap.map": "{\\"version\\":3,\\"sources\\":[\\"0\\"],\\"names\\":[\\"meaningOfLife\\",\\"Error\\"],\\"mappings\\":\\"AAAA,SAASA,gBAEP,MAAM,IAAIC,MADa\\",\\"file\\":\\"with-broken-sourcemap.js\\"}",
     "with-upstream-sourcemap.map": "{\\"version\\":3,\\"sources\\":[\\"/inner/first.js\\",\\"/inner/second.js\\",\\"/other/fourth.js\\",\\"/other/third.js\\"],\\"names\\":[\\"meaningOfLife\\",\\"Error\\",\\"boom\\",\\"somethingElse\\",\\"fourth\\",\\"third\\"],\\"mappings\\":\\"AAAA,SAAAA,gBAEA,MAAA,IAAAC,MADA,IAIA,SAAAC,OACA,MAAA,IAAAD,MAAA,QCNA,SAAAE,gBACA,MAAA,IAAAF,MAAA,kBCEA,SAAAG,SACA,MAAA,IAAAH,MAAA,UCJA,SAAAI,QACA,MAAA,IAAAJ,MAAA\\",\\"file\\":\\"with-upstream-sourcemap.js\\",\\"sourcesContent\\":[\\"function meaningOfLife() {\\\\n  var thisIsALongLocal = 42;\\\\n  throw new Error(thisIsALongLocal);\\\\n}\\\\n\\\\nfunction boom() {\\\\n  throw new Error('boom');\\\\n}\\\\n\\",\\"function somethingElse() {\\\\n  throw new Error(\\\\\\"somethign else\\\\\\");\\\\n}\\\\n\\",\\"\\\\n// Hello world\\\\n\\\\nfunction fourth(){\\\\n  throw new Error('fourth');\\\\n}\\\\n\\",\\"function third(){\\\\n  throw new Error(\\\\\\"oh no\\\\\\");\\\\n}\\\\n\\"]}",
   },
   "no-upstream-sourcemap.js": "function meaningOfLife(){throw new Error(42)}function boom(){throw new Error(\\"boom\\")}function somethingElse(){throw new Error(\\"somethign else\\")}function fourth(){throw new Error(\\"fourth\\")}function third(){throw new Error(\\"oh no\\")}
@@ -87,5 +95,7 @@ Object {
   "something.css": "#id {
     background: white;
 }",
+  "with-broken-sourcemap.js": "function meaningOfLife(){throw new Error(42)}
+//# sourceMappingURL=/maps/with-broken-sourcemap.map",
 }
 `;
diff --git a/test/fixtures/with-broken-sourcemap.js b/test/fixtures/with-broken-sourcemap.js
new file mode 100644
index 0000000..03af9ad
--- /dev/null
+++ b/test/fixtures/with-broken-sourcemap.js
@@ -0,0 +1,6 @@
+function meaningOfLife() {
+  var thisIsALongLocal = 42;
+  throw new Error(thisIsALongLocal);
+}
+
+//# sourceMappingURL=missing-sourcemap.map
\ No newline at end of file