diff --git a/test/input/pr-3040/expect.js b/test/input/pr-3040/expect.js
new file mode 100644
index 00000000..b911f3f8
--- /dev/null
+++ b/test/input/pr-3040/expect.js
@@ -0,0 +1,2 @@
+function _toConsumableArray(arr){if(Array.isArray(arr)){for(var i=0,arr2=Array(arr.length);i<arr.length;i++){arr2[i]=arr[i]}return arr2}else{return Array.from(arr)}}var _require=require("bar"),foo=_require.foo;var _require2=require("world"),hello=_require2.hello;foo.x.apply(foo,_toConsumableArray(foo.y(hello.z)));
+//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbImlucHV0Mi5qcyJdLCJuYW1lcyI6WyJyZXF1aXJlIiwiYXJyIl0sIm1hcHBpbmdzIjoiMEpBQWNBLEtBQVFDIiwic291cmNlc0NvbnRlbnQiOlsiY29uc3Qge2Zvb30gPSByZXF1aXJlKFwiYmFyXCIpO1xuY29uc3Qge2hlbGxvfSA9IHJlcXVpcmUoXCJ3b3JsZFwiKTtcblxuZm9vLngoLi4uZm9vLnkoaGVsbG8ueikpO1xuIl19
diff --git a/test/input/pr-3040/pipe.js b/test/input/pr-3040/pipe.js
deleted file mode 100644
index 298f7aa8..00000000
--- a/test/input/pr-3040/pipe.js
+++ /dev/null
@@ -1,9 +0,0 @@
-var fs = require("fs");
-
-// Timeout to offset uglify loading in the test suite
-var fileContents = fs.readFileSync("test/input/pr-3040/input.js");
-process.stdout.write(fileContents, "utf8");
-
-setTimeout(function() {
-    fs.writeFileSync("test/input/pr-3040/input.js.map", '{"version":3,"sources":["input2.js"],"names":[],"mappings":";;eAAc,QAAQ,KAAR,C;IAAP,G,YAAA,G;;gBACS,QAAQ,OAAR,C;IAAT,K,aAAA,K;;AAEP,IAAI,CAAJ,+BAAS,IAAI,CAAJ,CAAM,MAAM,CAAZ,CAAT","file":"input.js","sourcesContent":["const {foo} = require(\\"bar\\");\\nconst {hello} = require(\\"world\\");\\n\\nfoo.x(...foo.y(hello.z));\\n"]}');
-}, 100);
diff --git a/test/mocha/cli.js b/test/mocha/cli.js
index b7b09899..c52d2bb6 100644
--- a/test/mocha/cli.js
+++ b/test/mocha/cli.js
@@ -1,9 +1,9 @@
 var assert = require("assert");
 var exec = require("child_process").exec;
-var readFileSync = require("fs").readFileSync;
+var fs = require("fs");
 
 function read(path) {
-    return readFileSync(path, "utf8");
+    return fs.readFileSync(path, "utf8");
 }
 
 describe("bin/uglifyjs", function () {
@@ -94,27 +94,34 @@ describe("bin/uglifyjs", function () {
             done();
         });
     });
-    it("should not load the source map before it fully receives the JS source", function(done) {
+    it("Should not load source map before finish reading from STDIN", function(done) {
+        var mapFile = "tmp/input.js.map";
+        try {
+            fs.mkdirSync("./tmp");
+        } catch (e) {
+            if (e.code != "EEXIST") throw e;
+        }
+        try {
+            fs.unlinkSync(mapFile);
+        } catch (e) {
+            if (e.code != "ENOENT") throw e;
+        }
         var command = [
-            '"' + process.argv[0] + '" test/input/pr-3040/pipe.js |', uglifyjscmd,
-            "--source-map", "content=test/input/pr-3040/input.js.map",
+            uglifyjscmd,
+            "--source-map", "content=" + mapFile,
             "--source-map", "url=inline"
         ].join(" ");
-        
-        exec(command, function(err, stdout) {
+
+        var child = exec(command, function(err, stdout) {
             if (err) throw err;
-            
-            // Revert input file to initial state for future test validity
-            require("fs").writeFileSync("test/input/pr-3040/input.js.map", '{"version":3,"sources":["input2.js"],"names":["require","foo","hello","x","apply","_toConsumableArray","y","z"],"mappings":"kLAAcA,QAAQ,OAAfC,aAAAA,kBACSD,QAAQ,SAAjBE,gBAAAA,MAEPD,IAAIE,EAAJC,MAAAH,IAAAI,mBAASJ,IAAIK,EAAEJ,MAAMK","sourcesContent":["const {foo} = require(\\"bar\\");\\nconst {hello} = require(\\"world\\");\\n\\nfoo.x(...foo.y(hello.z));\\n"]}');
-            
-            assert.strictEqual(stdout, [
-                'function _toConsumableArray(arr){if(Array.isArray(arr)){for(var i=0,arr2=Array(arr.length);i<arr.length;i++){arr2[i]=arr[i]}return arr2}else{return Array.from(arr)}}var _require=require("bar"),foo=_require.foo;var _require2=require("world"),hello=_require2.hello;foo.x.apply(foo,_toConsumableArray(foo.y(hello.z)));\n',
-                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbImlucHV0Mi5qcyJdLCJuYW1lcyI6WyJyZXF1aXJlIiwiZm9vIiwiaGVsbG8iLCJ4IiwiYXBwbHkiLCJfdG9Db2",
-                "5zdW1hYmxlQXJyYXkiLCJ5IiwieiJdLCJtYXBwaW5ncyI6ImtMQUFjQSxRQUFRLE9BQWZDLGFBQUFBLGtCQUNTRCxRQUFRLFNBQWpCRSxnQkFBQUEsTUFFUEQsSUFBSUUsRUFBSkMsTUFBQUgsSUFBQUksbUJBQVNKLElBQUlLLEVBQUVKLE1B",
-                "QU1LIiwic291cmNlc0NvbnRlbnQiOlsiY29uc3Qge2Zvb30gPSByZXF1aXJlKFwiYmFyXCIpO1xuY29uc3Qge2hlbGxvfSA9IHJlcXVpcmUoXCJ3b3JsZFwiKTtcblxuZm9vLngoLi4uZm9vLnkoaGVsbG8ueikpO1xuIl19\n"
-            ].join(""));
+
+            assert.strictEqual(stdout, read("test/input/pr-3040/expect.js"));
             done();
         });
+        setTimeout(function() {
+            fs.copyFileSync("test/input/pr-3040/input.js.map", mapFile);
+            child.stdin.end(read("test/input/pr-3040/input.js"));
+        }, 1000);
     });
     it("Should work with --keep-fnames (mangle only)", function (done) {
         var command = uglifyjscmd + ' test/input/issue-1431/sample.js --keep-fnames -m';