diff --git a/src/api/python/z3/z3.py b/src/api/python/z3/z3.py
index 84a80ddf7..4234439d0 100644
--- a/src/api/python/z3/z3.py
+++ b/src/api/python/z3/z3.py
@@ -314,7 +314,7 @@ class AstRef(Z3PPObject):
             raise Z3Exception("Symbolic expressions cannot be cast to concrete Boolean values.")
 
     def sexpr(self):
-        """Return an string representing the AST node in s-expression notation.
+        """Return a string representing the AST node in s-expression notation.
 
         >>> x = Int('x')
         >>> ((x + 1)*x).sexpr()