diff --git a/src/api/python/z3/z3.py b/src/api/python/z3/z3.py
index 4ee5883ed..7e58a724c 100644
--- a/src/api/python/z3/z3.py
+++ b/src/api/python/z3/z3.py
@@ -6712,6 +6712,8 @@ class Optimize(Z3PPObject):
         """
         if _is_int(weight):
             weight = "%d" % weight
+        elif isinstance(weight, (float, double)):
+            weight = "%f" % weight
         if not isinstance(weight, str):
             raise Z3Exception("weight should be a string or an integer")
         if id is None: