diff --git a/src/index.js b/src/index.js
index 90627572..852e0193 100644
--- a/src/index.js
+++ b/src/index.js
@@ -366,7 +366,10 @@ module.exports = (
       // For some reason, auth0 returns "undefined"!
       // custom terser phase used over Webpack integration for this reason
       if (result.code !== undefined)
-        ({ code, map } = { code: result.code, map: result.map });
+        ({ code, map } = {
+          code: result.code,
+          map: sourceMap ? JSON.parse(result.map) : undefined
+        });
     }
 
     if (v8cache) {
diff --git a/test/index.test.js b/test/index.test.js
index 2dba9bda..f3015b24 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -11,17 +11,32 @@ for (const unitTest of fs.readdirSync(`${__dirname}/unit`)) {
       .trim()
       // Windows support
       .replace(/\r/g, "");
+    let expectedSoureMap;
+    try {
+      expectedSoureMap = fs
+        .readFileSync(`${testDir}/output${global.coverage ? '-coverage' : ''}.js.map`)
+        .toString()
+        .trim()
+        // Windows support
+        .replace(/\r/g, "");
+    } catch (_) {}
+
+    let opts;
+    try {
+      opts = fs.readFileSync(`${testDir}/opt.json`, 'utf8');
+      opts = JSON.parse(opts);
+    } catch (_) {}
 
     // set env variable so tsconfig-paths can find the config
     process.env.TS_NODE_PROJECT = `${testDir}/tsconfig.json`;
     // find the name of the input file (e.g input.ts)
     const inputFile = fs.readdirSync(testDir).find(file => file.includes("input"));
-    await ncc(`${testDir}/${inputFile}`, {
+    await ncc(`${testDir}/${inputFile}`, Object.assign({
       externals: {
         'externaltest': 'externalmapped'
       }
-    }).then(
-      async ({ code, assets }) => {
+    }, opts)).then(
+      async ({ code, assets, map }) => {
         const actual = code
           .trim()
           // Windows support
@@ -33,6 +48,20 @@ for (const unitTest of fs.readdirSync(`${__dirname}/unit`)) {
           fs.writeFileSync(`${testDir}/actual.js`, actual);
           throw e;
         }
+
+        if (map) {
+          const actualSourceMap = map
+            .trim()
+            // Windows support
+            .replace(/\r/g, "");
+          try {
+            expect(actualSourceMap).toBe(expectedSoureMap);
+          } catch (e) {
+            // useful for updating fixtures
+            fs.writeFileSync(`${testDir}/actual.js.map`, actualSourceMap);
+            throw e;
+          }
+        }
       }
     );
   });
diff --git a/test/unit/minify/input.js b/test/unit/minify/input.js
new file mode 100644
index 00000000..74b15e55
--- /dev/null
+++ b/test/unit/minify/input.js
@@ -0,0 +1,2 @@
+const foobar = 'qux'
+exports.foobar = foobar
diff --git a/test/unit/minify/opt.json b/test/unit/minify/opt.json
new file mode 100644
index 00000000..c66df06a
--- /dev/null
+++ b/test/unit/minify/opt.json
@@ -0,0 +1,5 @@
+{
+  "minify": true,
+  "sourceMap": true,
+  "sourceMapRegister": false
+}
diff --git a/test/unit/minify/output-coverage.js b/test/unit/minify/output-coverage.js
new file mode 100644
index 00000000..0ee64ce2
--- /dev/null
+++ b/test/unit/minify/output-coverage.js
@@ -0,0 +1,2 @@
+module.exports=function(r,e){"use strict";var t={};function __webpack_require__(e){if(t[e]){return t[e].exports}var _=t[e]={i:e,l:false,exports:{}};r[e].call(_.exports,_,_.exports,__webpack_require__);_.l=true;return _.exports}__webpack_require__.ab=__dirname+"/";function startup(){return __webpack_require__(894)}return startup()}({894:function(r,e){const t="qux";e.foobar=t}});
+//# sourceMappingURL=index.js.map
\ No newline at end of file
diff --git a/test/unit/minify/output-coverage.js.map b/test/unit/minify/output-coverage.js.map
new file mode 100644
index 00000000..36d3f443
--- /dev/null
+++ b/test/unit/minify/output-coverage.js.map
@@ -0,0 +1 @@
+{"version":3,"sources":["/webpack/bootstrap","../test/unit/minify/input.js"],"names":["installedModules","__webpack_require__","moduleId","exports","module","i","l","modules","call","ab","__dirname","startup","foobar"],"mappings":"0CACA,IAAAA,EAAA,GAGA,SAAAC,oBAAAC,GAGA,GAAAF,EAAAE,GAAA,CACA,OAAAF,EAAAE,GAAAC,QAGA,IAAAC,EAAAJ,EAAAE,GAAA,CACAG,EAAAH,EACAI,EAAA,MACAH,QAAA,IAIAI,EAAAL,GAAAM,KAAAJ,EAAAD,QAAAC,EAAAA,EAAAD,QAAAF,qBAGAG,EAAAE,EAAA,KAGA,OAAAF,EAAAD,QAIAF,oBAAAQ,GAAAC,UAAA,IAGA,SAAAC,UAEA,OAAAV,oBAAA,KAIA,OAAAU,8BCrCA,MAAAC,EAAA,MACAT,EAAOS,OAAAA","file":"index.js","sourcesContent":[" \t// The module cache\n \tvar installedModules = {};\n\n \t// The require function\n \tfunction __webpack_require__(moduleId) {\n\n \t\t// Check if module is in cache\n \t\tif(installedModules[moduleId]) {\n \t\t\treturn installedModules[moduleId].exports;\n \t\t}\n \t\t// Create a new module (and put it into the cache)\n \t\tvar module = installedModules[moduleId] = {\n \t\t\ti: moduleId,\n \t\t\tl: false,\n \t\t\texports: {}\n \t\t};\n\n \t\t// Execute the module function\n \t\tmodules[moduleId].call(module.exports, module, module.exports, __webpack_require__);\n\n \t\t// Flag the module as loaded\n \t\tmodule.l = true;\n\n \t\t// Return the exports of the module\n \t\treturn module.exports;\n \t}\n\n\n \t__webpack_require__.ab = __dirname + \"/\";\n\n \t// the startup function\n \tfunction startup() {\n \t\t// Load entry module and return exports\n \t\treturn __webpack_require__(894);\n \t};\n\n \t// run startup\n \treturn startup();\n","const foobar = 'qux'\nexports.foobar = foobar\n"]}
\ No newline at end of file
diff --git a/test/unit/minify/output.js b/test/unit/minify/output.js
new file mode 100644
index 00000000..08b31d1e
--- /dev/null
+++ b/test/unit/minify/output.js
@@ -0,0 +1,2 @@
+module.exports=function(r,e){"use strict";var t={};function __webpack_require__(e){if(t[e]){return t[e].exports}var _=t[e]={i:e,l:false,exports:{}};r[e].call(_.exports,_,_.exports,__webpack_require__);_.l=true;return _.exports}__webpack_require__.ab=__dirname+"/";function startup(){return __webpack_require__(657)}return startup()}({657:function(r,e){const t="qux";e.foobar=t}});
+//# sourceMappingURL=index.js.map
\ No newline at end of file
diff --git a/test/unit/minify/output.js.map b/test/unit/minify/output.js.map
new file mode 100644
index 00000000..96aeb2e4
--- /dev/null
+++ b/test/unit/minify/output.js.map
@@ -0,0 +1 @@
+{"version":3,"sources":["/webpack/bootstrap","../test/unit/minify/input.js"],"names":["installedModules","__webpack_require__","moduleId","exports","module","i","l","modules","call","ab","__dirname","startup","foobar"],"mappings":"0CACA,IAAAA,EAAA,GAGA,SAAAC,oBAAAC,GAGA,GAAAF,EAAAE,GAAA,CACA,OAAAF,EAAAE,GAAAC,QAGA,IAAAC,EAAAJ,EAAAE,GAAA,CACAG,EAAAH,EACAI,EAAA,MACAH,QAAA,IAIAI,EAAAL,GAAAM,KAAAJ,EAAAD,QAAAC,EAAAA,EAAAD,QAAAF,qBAGAG,EAAAE,EAAA,KAGA,OAAAF,EAAAD,QAIAF,oBAAAQ,GAAAC,UAAA,IAGA,SAAAC,UAEA,OAAAV,oBAAA,KAIA,OAAAU,8BCrCA,MAAAC,EAAA,MACAT,EAAOS,OAAAA","file":"index.js","sourcesContent":[" \t// The module cache\n \tvar installedModules = {};\n\n \t// The require function\n \tfunction __webpack_require__(moduleId) {\n\n \t\t// Check if module is in cache\n \t\tif(installedModules[moduleId]) {\n \t\t\treturn installedModules[moduleId].exports;\n \t\t}\n \t\t// Create a new module (and put it into the cache)\n \t\tvar module = installedModules[moduleId] = {\n \t\t\ti: moduleId,\n \t\t\tl: false,\n \t\t\texports: {}\n \t\t};\n\n \t\t// Execute the module function\n \t\tmodules[moduleId].call(module.exports, module, module.exports, __webpack_require__);\n\n \t\t// Flag the module as loaded\n \t\tmodule.l = true;\n\n \t\t// Return the exports of the module\n \t\treturn module.exports;\n \t}\n\n\n \t__webpack_require__.ab = __dirname + \"/\";\n\n \t// the startup function\n \tfunction startup() {\n \t\t// Load entry module and return exports\n \t\treturn __webpack_require__(657);\n \t};\n\n \t// run startup\n \treturn startup();\n","const foobar = 'qux'\nexports.foobar = foobar\n"]}
\ No newline at end of file