diff --git a/requirements-dev.in b/requirements-dev.in
index 49324f7..e1b78b7 100644
--- a/requirements-dev.in
+++ b/requirements-dev.in
@@ -14,4 +14,4 @@
 # limitations under the License.
 
 git+https://osm.etsi.org/gerrit/osm/IM.git@master#egg=osm-im
--r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+-r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
diff --git a/requirements-dev.txt b/requirements-dev.txt
index c61b32e..195078d 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -16,32 +16,32 @@
 #######################################################################################
 bitarray==2.5.1
     # via
-    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
     #   pyangbind
 enum34==1.1.10
     # via
-    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
     #   pyangbind
 lxml==4.9.0
     # via
-    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
     #   pyang
     #   pyangbind
 osm-im @ git+https://osm.etsi.org/gerrit/osm/IM.git@master
     # via -r requirements-dev.in
 pyang==2.5.3
     # via
-    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
     #   pyangbind
 pyangbind==0.8.1
-    # via -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+    # via -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
 pyyaml==5.4.1
-    # via -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+    # via -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
 regex==2022.6.2
     # via
-    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
     #   pyangbind
 six==1.16.0
     # via
-    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+    #   -r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
     #   pyangbind
diff --git a/tox.ini b/tox.ini
index 604d3e2..eea8257 100644
--- a/tox.ini
+++ b/tox.ini
@@ -54,7 +54,7 @@
 
 #######################################################################################
 [testenv:flake8]
-deps = flake8
+deps = flake8==5.0.4
 commands =
         flake8 osmclient/ setup.py