diff --git a/gns3server/run.py b/gns3server/run.py
index 47f5067d..98fd1c27 100644
--- a/gns3server/run.py
+++ b/gns3server/run.py
@@ -236,7 +236,7 @@ def run():
             return
         log.info("HTTP authentication is enabled with username '{}'".format(user))
 
-    # we only support Python 3 version >= 3.5
+    # we only support Python 3 version >= 3.5.3
     if sys.version_info < (3, 5, 3):
         raise SystemExit("Python 3.5.3 or higher is required")
 
diff --git a/requirements.txt b/requirements.txt
index 0d77d996..81ff0d1b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,4 @@
+yarl==1.3.0  # yarl 1.4+ requires Python 3.6+ (needed by aiohttp and aiohttp-cors)
 jsonschema==2.6.0  # pyup: ignore
 aiohttp==3.6.2
 aiohttp-cors==0.7.0