diff --git a/taggy.cabal b/taggy.cabal
index 30e0d46..fe78a22 100644
--- a/taggy.cabal
+++ b/taggy.cabal
@@ -60,6 +60,7 @@ library
                        text >= 1,
                        attoparsec >=0.11,
                        vector >=0.7,
+                       containers,
                        unordered-containers >= 0.2
   hs-source-dirs:      src
   default-language:    Haskell2010