diff --git a/tests/test-rebase-obsolete.t b/tests/test-rebase-obsolete.t
--- a/tests/test-rebase-obsolete.t
+++ b/tests/test-rebase-obsolete.t
@@ -902,7 +902,7 @@ rebase source is obsoleted (issue5198)
   $ hg up 9520eea781bc
   1 files updated, 0 files merged, 2 files removed, 0 files unresolved
   $ echo 1 >> E
-  $ hg commit --amend -m "E'"
+  $ hg commit --amend -m "E'" -d "0 0"
   $ hg log -G
   @  9:69abe8906104 E'
   |
diff --git a/tests/test-subrepo-git.t b/tests/test-subrepo-git.t
--- a/tests/test-subrepo-git.t
+++ b/tests/test-subrepo-git.t
@@ -2,6 +2,11 @@
 
 make git commits repeatable
 
+  $ cat >> $HGRCPATH <<EOF
+  > [defaults]
+  > commit = -d "0 0"
+  > EOF
+
   $ echo "[core]" >> $HOME/.gitconfig
   $ echo "autocrlf = false" >> $HOME/.gitconfig
   $ GIT_AUTHOR_NAME='test'; export GIT_AUTHOR_NAME