diff --git a/scripts/scm-prompt.sh b/scripts/scm-prompt.sh
index c5460683b4..237eacfda3 100644
--- a/scripts/scm-prompt.sh
+++ b/scripts/scm-prompt.sh
@@ -208,10 +208,13 @@ _scm_prompt()
 
 _dotfiles_scm_info() {
   local fmt
+  fmt=$1
   if [[ -z "$fmt" ]]; then
     if [[ -n "$WANT_OLD_SCM_PROMPT" ]]; then
       fmt="%s"
+    else
+      fmt=' (%s)'
     fi
   fi
-  _scm_prompt $fmt
+  _scm_prompt "$fmt"
 }
diff --git a/tests/test-scm-prompt-compat.t b/tests/test-scm-prompt-compat.t
index 039ad1153a..49e706c968 100644
--- a/tests/test-scm-prompt-compat.t
+++ b/tests/test-scm-prompt-compat.t
@@ -26,3 +26,12 @@ Test old mode
   5cad84d (no-eol)
   $ cmd hg book active
   active (no-eol)
+
+Test format string
+  $ oldcmd() {
+  >   "$@"
+  >   _dotfiles_scm_info "g g %s g g\n"
+  > }
+  $ hg init repo
+  $ oldcmd cd repo
+  g g empty g g