diff --git a/zlib-ada.spec b/zlib-ada.spec
index c9294f2..5b03d1c 100644
--- a/zlib-ada.spec
+++ b/zlib-ada.spec
@@ -110,7 +110,7 @@ cp %{SOURCE1} .
 ###########
 
 %build
-gprbuild %{GPRbuild_flags} -XVERSION=%{upstream_version} \
+gprbuild %{GPRbuild_flags} -XVERSION=%{upstream_commit_date} \
          -XDESTDIR=build_target -XLDFLAGS='%{__global_ldflags}' \
          -P build_zlib_ada.gpr