diff --git a/gzip.spec b/gzip.spec
index 5d8a4cd..c9b9e02 100644
--- a/gzip.spec
+++ b/gzip.spec
@@ -66,8 +66,8 @@ profile_gzip()
 {
   tmpfile=$(mktemp)
   trap "rm -f $tmpfile $tmpfile.gz" EXIT
-  tar -cf $tmpfile %{_prefix} || true
-  time ./gzip $tmpfile
+  tar -cfd %{SOURCE0} > $tmpfile || true
+  time ./gzip < $tmpfile > $tmpfile.gz
   time ./gzip -d < $tmpfile.gz > /dev/null
 }
 %if %{do_profiling}