diff --git a/src/chunk-manifest-webpack-plugin.js b/src/chunk-manifest-webpack-plugin.js
index fdd8770..e649780 100644
--- a/src/chunk-manifest-webpack-plugin.js
+++ b/src/chunk-manifest-webpack-plugin.js
@@ -24,7 +24,7 @@ class ChunkManifestPlugin {
 
     compiler.plugin("this-compilation", function(compilation) {
       const mainTemplate = compilation.mainTemplate;
-      mainTemplate.plugin("require-ensure", function(_, chunk, hash) {
+      mainTemplate.plugin("require-ensure", function(source, chunk, hash) {
         const filename =
           this.outputOptions.chunkFilename || this.outputOptions.filename;
 
@@ -61,13 +61,13 @@ class ChunkManifestPlugin {
           );
         }
 
-        return _;
+        return source;
       });
     });
 
     compiler.plugin("compilation", function(compilation) {
       compilation.mainTemplate.plugin("require-ensure", function(
-        _,
+        source,
         chunk,
         hash,
         chunkIdVariableName
@@ -75,10 +75,13 @@ class ChunkManifestPlugin {
         if (oldChunkFilename) {
           this.outputOptions.chunkFilename = oldChunkFilename;
         }
-        return _.replace(
+
+        const updatedSource = source.replace(
           /"__CHUNK_MANIFEST__"/,
           `window["${manifestVariable}"][${chunkIdVariableName}]`
         );
+
+        return updatedSource;
       });
     });
   }
diff --git a/test/plugin-runtime-replacement-test.js b/test/plugin-runtime-replacement-test.js
new file mode 100644
index 0000000..42da678
--- /dev/null
+++ b/test/plugin-runtime-replacement-test.js
@@ -0,0 +1,69 @@
+import test from "ava";
+
+import ChunkManifestPlugin from "../src/chunk-manifest-webpack-plugin";
+
+/*compiler.plugin("compilation", function(compilation) {
+      compilation.mainTemplate.plugin("require-ensure", function(
+        source,
+        chunk,
+        hash,
+        chunkIdVariableName
+      ) {
+        if (oldChunkFilename) {
+          this.outputOptions.chunkFilename = oldChunkFilename;
+        }
+        return source.replace(
+          /"__CHUNK_MANIFEST__"/,
+          `window["${manifestVariable}"][${chunkIdVariableName}]`
+        );
+      });
+    });*/
+
+test.cb("replace runtime with lookup", t => {
+  const chunkIdVariableName = "a-chunk-id-variable";
+  const manifestVariable = "manifest-variable";
+  const placeholder = `"__CHUNK_MANIFEST__"`;
+
+  const runtimeSource = [
+    "runtime-source-start",
+    placeholder,
+    ";",
+    "runtime-source-end"
+  ];
+
+  let expected = [...runtimeSource];
+  expected[1] = `window["${manifestVariable}"][${chunkIdVariableName}]`;
+
+  const compilationPluginEvent = (compilationEvent, ensure) => {
+    if (compilationEvent === "require-ensure") {
+      const updatedSource = ensure(
+        runtimeSource.join(""),
+        undefined,
+        undefined,
+        chunkIdVariableName
+      );
+      t.is(updatedSource, expected.join(""));
+      t.end();
+    }
+  };
+
+  const pluginEvent = (event, compile) => {
+    if (event === "compilation") {
+      const compilation = {
+        mainTemplate: {
+          plugin: compilationPluginEvent
+        }
+      };
+      compile(compilation);
+    }
+  };
+
+  const fakeCompiler = { plugin: pluginEvent };
+
+  const plugin = new ChunkManifestPlugin({
+    manifestVariable
+  });
+
+  plugin.plugins = [{ apply: () => {} }];
+  plugin.apply(fakeCompiler);
+});