diff --git a/openapi_schema_validator/_format.py b/openapi_schema_validator/_format.py
index 35f0653..415f556 100644
--- a/openapi_schema_validator/_format.py
+++ b/openapi_schema_validator/_format.py
@@ -90,7 +90,7 @@ def is_uuid(instance):
     if isinstance(instance, binary_type):
         instance = instance.decode()
 
-    return text_type(UUID(instance)) == instance
+    return text_type(UUID(instance)).lower() == instance.lower()
 
 
 def is_password(instance):