diff --git a/pcsx2/CDVD/GzippedFileReader.cpp b/pcsx2/CDVD/GzippedFileReader.cpp
index 247e58e5f1..d2a996520d 100644
--- a/pcsx2/CDVD/GzippedFileReader.cpp
+++ b/pcsx2/CDVD/GzippedFileReader.cpp
@@ -80,7 +80,7 @@ static void WriteIndexToFile(Access* index, const char* filename)
 		return;
 	}
 
-	auto fp = FileSystem::OpenManagedCFile(filename, "rb");
+	auto fp = FileSystem::OpenManagedCFile(filename, "wb");
 	if (!fp)
 		return;