diff --git a/CHANGELOG.md b/CHANGELOG.md
index eecac4be..1e915dd4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Changed
+
+- `aimock-pytest` 0.5.3 now defaults to `@copilotkit/aimock` 1.39.0.
+
 ## [1.39.0] - 2026-08-18
 
 ### Added
diff --git a/packages/aimock-pytest/pyproject.toml b/packages/aimock-pytest/pyproject.toml
index 7d30cff1..1072e224 100644
--- a/packages/aimock-pytest/pyproject.toml
+++ b/packages/aimock-pytest/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "aimock-pytest"
-version = "0.5.2"
+version = "0.5.3"
 description = "pytest fixtures for aimock — mock LLM APIs, multimedia, MCP, A2A, AG-UI, vector DBs, and more"
 readme = "README.md"
 requires-python = ">=3.10"