diff --git a/src/axolotl/utils/schemas/config.py b/src/axolotl/utils/schemas/config.py
index d85697d10..3a035867f 100644
--- a/src/axolotl/utils/schemas/config.py
+++ b/src/axolotl/utils/schemas/config.py
@@ -1335,7 +1335,7 @@ class AxolotlConfigWCapabilities(AxolotlInputConfig):
                 )[0]
 
             if version.parse(transformers_version) < version.parse("4.45.1"):
-                LOG.warning(
+                raise ValueError(
                     "Transformers version < 4.45.1 is not supported with flex attention. "
                 )