diff --git a/src/api/ml/z3.mli b/src/api/ml/z3.mli
index 0207a53ed..4f10b275a 100644
--- a/src/api/ml/z3.mli
+++ b/src/api/ml/z3.mli
@@ -1912,7 +1912,7 @@ sig
   (* union of regular expressions *)
   val mk_re_union : context -> Expr.expr list -> Expr.expr 
 
-  (* concatenation of regular expressions* )
+  (* concatenation of regular expressions *)
   val mk_re_concat : context -> Expr.expr list -> Expr.expr 
   
   (* regular expression for the range between two characters *)