diff --git a/UnleashClient/constants.py b/UnleashClient/constants.py
index b711cfb..21982bb 100644
--- a/UnleashClient/constants.py
+++ b/UnleashClient/constants.py
@@ -6,7 +6,7 @@
 REQUEST_TIMEOUT = 30
 REQUEST_RETRIES = 3
 METRIC_LAST_SENT_TIME = "mlst"
-CLIENT_SPEC_VERSION = "5.1.0"
+CLIENT_SPEC_VERSION = "5.1.9"
 
 # =Unleash=
 APPLICATION_HEADERS = {