diff --git a/src/build.sh b/src/build.sh
index e3f0242..b8375d8 100644
--- a/src/build.sh
+++ b/src/build.sh
@@ -14,7 +14,7 @@ echo $BUILDPATH
 
 #unzip this or something
 curl -RO "$DOWNLOAD"
-tar -xzf "firefox-$VERSION.source.tar.xz"
+tar -xJf "firefox-$VERSION.source.tar.xz"
 
 
 cd "firefox-$VERSION.source/js/src"