diff --git a/README.md b/README.md
index 6be3e46..9371197 100644
--- a/README.md
+++ b/README.md
@@ -158,7 +158,7 @@ more details.
 
 |Variable|Default|Meaning
 |--------|-------|-------|
-|`BULLETTRAIN_CUSTOM_MSG`|`false`|Free segment you can put a custom message
+|`BULLETTRAIN_CUSTOM_MSG`|`false`|Free segment you can put a custom message which will be eval'ed for every prompt
 |`BULLETTRAIN_CUSTOM_BG`|`black`|Background color
 |`BULLETTRAIN_CUSTOM_FG`|`black`|Foreground color
 
diff --git a/bullet-train.zsh-theme b/bullet-train.zsh-theme
index 8314623..dbfd55a 100644
--- a/bullet-train.zsh-theme
+++ b/bullet-train.zsh-theme
@@ -380,7 +380,9 @@ prompt_custom() {
     return
   fi
 
-  prompt_segment $BULLETTRAIN_CUSTOM_BG $BULLETTRAIN_CUSTOM_FG "${BULLETTRAIN_CUSTOM_MSG}"
+  local custom_msg
+  eval custom_msg=$BULLETTRAIN_CUSTOM_MSG
+  [[ -n "${custom_msg}" ]] && prompt_segment $BULLETTRAIN_CUSTOM_BG $BULLETTRAIN_CUSTOM_FG "${custom_msg}"
 }
 
 # Git