diff --git a/setup.cfg b/setup.cfg
index fab77f8..2d7e626 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -45,7 +45,7 @@ install_requires =
 dev =
     # freezegun 1.2.2 fixed pytest timing interference.
     freezegun>=1.2.2
-    requests-mock[fixture]
+    requests-mock[fixture]==1.11.0
 
 [options.entry_points]
 pytest11 =