diff --git a/outlines/text/json_schema.py b/outlines/text/json_schema.py
index 0c597b84d..614227531 100644
--- a/outlines/text/json_schema.py
+++ b/outlines/text/json_schema.py
@@ -63,6 +63,9 @@ def to_regex(resolver: Resolver, instance: dict):
     - Handle types defined as a list
     - Handle constraints on numbers
     - Handle special patterns: `date`, `uri`, etc.
+    - Handle optional fields (not in `required`)
+
+    This does not support recursive definitions.
 
     Parameters
     ----------
@@ -116,12 +119,14 @@ def to_regex(resolver: Resolver, instance: dict):
     # The enum keyword is used to restrict a value to a fixed set of values. It
     # must be an array with at least one element, where each element is unique.
     elif "enum" in instance:
-        if instance["type"] == "string":
-            choices = [f'"{re.escape(choice)}"' for choice in instance["enum"]]
-            return f"({'|'.join(choices)})"
-        else:
-            choices = [re.escape(str(choice)) for choice in instance["enum"]]
-            return f"({'|'.join(choices)})"
+        choices = []
+        for choice in instance["enum"]:
+            if type(choice) in [int, float, bool, None]:
+                choices.append(re.escape(str(choice)))
+            elif type(choice) == str:
+                choices.append(f'"{re.escape(choice)}"')
+
+        return f"({'|'.join(choices)})"
 
     elif "$ref" in instance:
         path = f"{instance['$ref']}"
@@ -134,8 +139,8 @@ def to_regex(resolver: Resolver, instance: dict):
     # the name of one of the basic types, and each element is unique. In this
     # case, the JSON snippet is valid if it matches any of the given types.
     elif "type" in instance:
-        type = instance["type"]
-        if type == "string":
+        instance_type = instance["type"]
+        if instance_type == "string":
             if "maxLength" in instance or "minLength" in instance:
                 max_length = instance.get("maxLength", "")
                 min_length = instance.get("minLength", "")
@@ -156,13 +161,13 @@ def to_regex(resolver: Resolver, instance: dict):
             else:
                 return type_to_regex["string"]
 
-        elif type == "number":
+        elif instance_type == "number":
             return type_to_regex["number"]
 
-        elif type == "integer":
+        elif instance_type == "integer":
             return type_to_regex["integer"]
 
-        elif type == "array":
+        elif instance_type == "array":
             if "items" in instance:
                 items_regex = to_regex(resolver, instance["items"])
                 return rf"\[({items_regex})(,({items_regex}))*\]"
@@ -180,17 +185,19 @@ def to_regex(resolver: Resolver, instance: dict):
                 regexes = [to_regex(resolver, t) for t in types]
                 return rf"\[({'|'.join(regexes)})(,({'|'.join(regexes)}))*\]"
 
-        elif type == "boolean":
+        elif instance_type == "boolean":
             return type_to_regex["boolean"]
 
-        elif type == "null":
+        elif instance_type == "null":
             return type_to_regex["null"]
 
-        elif isinstance(type, list):
+        elif isinstance(instance_type, list):
             # Here we need to make the choice to exclude generating an object
             # if the specification of the object is not give, even though a JSON
             # object that contains an object here would be valid under the specification.
-            regexes = [to_regex(resolver, {"type": t}) for t in type if t != "object"]
+            regexes = [
+                to_regex(resolver, {"type": t}) for t in instance_type if t != "object"
+            ]
             return rf"({'|'.join(regexes)})"
 
     raise NotImplementedError(