diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index a967f81ece9..ee115aab609 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -430,6 +430,10 @@ unpackFile() {
     header "unpacking source archive $curSrc" 3
 
     case "$curSrc" in
+        *.tar.xz | *.tar.lzma)
+            # Don't rely on tar knowing about .xz.
+            xz -d < $curSrc | tar xv -
+            ;;
         *.tar | *.tar.* | *.tgz | *.tbz2)
             # GNU tar can automatically select the decompression method
             # (info "(tar) gzip").