diff --git a/slack-web.cabal b/slack-web.cabal
--- a/slack-web.cabal
+++ b/slack-web.cabal
@@ -1,8 +1,8 @@
 name: slack-web
-version: 0.2.0.9
+version: 0.2.0.10
 
 build-type: Simple
-cabal-version: 1.21
+cabal-version: 1.20
 
 license: MIT
 license-file: LICENSE.md
@@ -48,7 +48,7 @@
     , base >= 4.11 && < 4.13
     , containers
     , http-api-data >= 0.3 && < 0.5
-    , http-client >= 0.5 && < 0.6
+    , http-client >= 0.5 && < 0.7
     , http-client-tls >= 0.3 && < 0.4
     , servant >= 0.12 && < 0.16
     , servant-client >= 0.12 && < 0.16
diff --git a/src/Web/Slack/MessageParser.hs b/src/Web/Slack/MessageParser.hs
--- a/src/Web/Slack/MessageParser.hs
+++ b/src/Web/Slack/MessageParser.hs
@@ -56,6 +56,7 @@
 
 #if MIN_VERSION_megaparsec(7,0,0)
 #else
+anySingle :: ParsecT MegaparsecError Text Identity (Token Text)
 anySingle = anyChar
 #endif