diff --git a/themes/base.theme.bash b/themes/base.theme.bash
index a18c3729..e27cd5f1 100644
--- a/themes/base.theme.bash
+++ b/themes/base.theme.bash
@@ -125,8 +125,8 @@ function scm_prompt_info_common {
   fi
 
   # TODO: consider adding minimal status information for hg and svn
-  [[ ${SCM} == ${SCM_HG} ]] && hg_prompt_info && return
-  [[ ${SCM} == ${SCM_SVN} ]] && svn_prompt_info && return
+  { [[ ${SCM:-} == ${SCM_HG} ]] && hg_prompt_info && return; } || true
+  { [[ ${SCM:-} == ${SCM_SVN} ]] && svn_prompt_info && return; } || true
 }
 
 function git_prompt_minimal_info {