diff --git a/src/Niv/GitHub.hs b/src/Niv/GitHub.hs
index a9d57c7..1adcbb0 100644
--- a/src/Niv/GitHub.hs
+++ b/src/Niv/GitHub.hs
@@ -33,7 +33,7 @@ githubUpdate prefetch latestRev ghRepo = proc () -> do
       (useOrSet "url_template" <<< completeSpec) <+> (load "url_template") -<
       ()
     url <- update "url" -< urlTemplate
-    let isTar = ("tar.gz" `T.isSuffixOf`) <$> url
+    let isTar = (\u -> "tar.gz" `T.isSuffixOf` u || ".tgz" `T.isSuffixOf` u) <$> url
     useOrSet "type" -< bool "file" "tarball" <$> isTar :: Box T.Text
     let doUnpack = isTar
     _sha256 <- update "sha256" <<< run (\(up, u) -> prefetch up u) -< (,) <$> doUnpack <*> url