diff --git a/packages/cmk-plugins/cmk/plugins/aws/special_agent/agent_aws.py b/packages/cmk-plugins/cmk/plugins/aws/special_agent/agent_aws.py
index f021c2b21d1..e3af638aa1c 100644
--- a/packages/cmk-plugins/cmk/plugins/aws/special_agent/agent_aws.py
+++ b/packages/cmk-plugins/cmk/plugins/aws/special_agent/agent_aws.py
@@ -297,6 +297,9 @@ def datetime_serializer(obj):
     """Custom serializer to pass to json dump functions"""
     if isinstance(obj, datetime):
         return str(obj)
+    if isinstance(obj, bytes):
+        # e.g. WAFv2 ByteMatchStatement.SearchString is returned by boto3 as bytes
+        return obj.decode("utf-8", errors="replace")
     # fall back to json default behaviour:
     raise TypeError("%r is not JSON serializable" % obj)