diff --git a/build/lib/compilation.js b/build/lib/compilation.js
index f26b7ac..15d930c 100644
--- a/build/lib/compilation.js
+++ b/build/lib/compilation.js
@@ -109,3 +109,3 @@ function compileTask(src, out, build) {
             mangleStream = es.through(function write(data) {
-                const newContents = newContentsByFileName.get(data.path);
+                const newContents = newContentsByFileName.get(data.path.replace(/\\/g, '/'));
                 if (newContents !== undefined) {
diff --git a/build/lib/compilation.ts b/build/lib/compilation.ts
index 2cc04d2..9029c62 100644
--- a/build/lib/compilation.ts
+++ b/build/lib/compilation.ts
@@ -128,3 +128,3 @@ export function compileTask(src: string, out: string, build: boolean): () => Nod
 			mangleStream = es.through(function write(data: File) {
-				const newContents = newContentsByFileName.get(data.path);
+				const newContents = newContentsByFileName.get(data.path.replace(/\\/g, '/'));
 				if (newContents !== undefined) {