diff --git a/moto/core/responses.py b/moto/core/responses.py
index 5fda815e7..e0b2e9a5b 100644
--- a/moto/core/responses.py
+++ b/moto/core/responses.py
@@ -142,7 +142,7 @@ class BaseResponse(_TemplateEnvironmentMixin):
             # Headers are case-insensitive. Probably a better way to do this.
             match = self.headers.get('x-amz-target') or self.headers.get('X-Amz-Target')
             if match:
-                action = match.split(".")[1]
+                action = match.split(".")[-1]
 
         action = camelcase_to_underscores(action)
         method_names = method_names_from_class(self.__class__)