check for compiler.hooks

Author: SimulatedGREG

lib/virtual.js

@@ -32,10 +32,16 @@ function VirtualModulesPlugin(compiler) {
 		};
 	}
 
-	compiler.hooks.watchRun.tapAsync('VirtualModulesPlugin', (watcher, callback) => {
+	const watchRunHook = (watcher, callback) => {
 		this._watcher = watcher.compiler || watcher;
 		callback();
-	});
+	};
+
+	if (compiler.hooks) {
+		compiler.hooks.watchRun.tapAsync('VirtualModulesPlugin', watchRunHook);
+	} else {
+		compiler.plugin('watch-run', watchRunHook);
+	}
 }
 
 VirtualModulesPlugin.prototype.writeModule = function(filePath, contents) {