diff --git a/.changeset/lovely-queens-marry.md b/.changeset/lovely-queens-marry.md
new file mode 100644
index 00000000000..23331634a83
--- /dev/null
+++ b/.changeset/lovely-queens-marry.md
@@ -0,0 +1,5 @@
+---
+"electron-updater": patch
+---
+
+fix(electron-updater): relax multipart boundary regex to allow no space
diff --git a/packages/electron-updater/src/differentialDownloader/multipleRangeDownloader.ts b/packages/electron-updater/src/differentialDownloader/multipleRangeDownloader.ts
index b4255e1064c..9d405cf002d 100644
--- a/packages/electron-updater/src/differentialDownloader/multipleRangeDownloader.ts
+++ b/packages/electron-updater/src/differentialDownloader/multipleRangeDownloader.ts
@@ -97,7 +97,7 @@ function doExecuteTasks(differentialDownloader: DifferentialDownloader, options:
     }
 
     const contentType = safeGetHeader(response, "content-type")
-    const m = /^multipart\/.+?\s*;\s*boundary=(?:"([^"]+)"|([^\s";]+))\s*$/i.exec(contentType)
+    const m = /^multipart\/.+?\s*;[\s]*boundary=(?:"([^"]+)"|([^\s";]+))\s*$/i.exec(contentType)
     if (m == null) {
       reject(new Error(`Content-Type "multipart/byteranges" is expected, but got "${contentType}"`))
       return