diff --git a/client/utils/buildChallenges.js b/client/utils/buildChallenges.js
index c704a5f1db..b16d445914 100644
--- a/client/utils/buildChallenges.js
+++ b/client/utils/buildChallenges.js
@@ -17,7 +17,8 @@ exports.replaceChallengeNode = () => {
   return async function replaceChallengeNode(filePath) {
     // get the meta so that challengeOrder is accurate
     const blockNameRe = /\d\d-[-\w]+\/([^/]+)\//;
-    const blockName = filePath.match(blockNameRe)[1];
+    const posix = path.normalize(filePath).split(path.sep).join(path.posix.sep);
+    const blockName = posix.match(blockNameRe)[1];
     const metaPath = path.resolve(
       __dirname,
       `../../curriculum/challenges/_meta/${blockName}/meta.json`