diff --git a/src/api/python/z3/z3.py b/src/api/python/z3/z3.py
index dba147779..16efc2f06 100644
--- a/src/api/python/z3/z3.py
+++ b/src/api/python/z3/z3.py
@@ -1100,7 +1100,7 @@ def _coerce_expr_merge(s, a):
             if z3_debug():
                 _z3_assert(s1.ctx == s.ctx, "context mismatch")
                 _z3_assert(False, "sort mismatch")
-    elif s:
+    elif s is not None:
         return s
     elif isinstance(a, str):
         return StringSort()