diff --git a/requirements.txt b/requirements.txt
index 920fdd1b30..0dc7ce4eec 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,6 +2,8 @@ xmltodict<0.12.0; python_version == '3.3'
 xmltodict==0.12; python_version != '3.3'
 pytz
 praw>=4.0.0,<6.0.0
+# transitive dependency of praw; v0.18 introduced f-string syntax
+update-checker<0.18; python_version < '3.6'
 geoip2<3.0; python_version <= '3.5' and python_version != '2.7'
 geoip2>=3.0,<4.0; python_version == '2.7'
 geoip2>=4.0,<5.0; python_version >= '3.6'