diff --git a/pkgs/development/tools/parsing/alex/3.1.2.nix b/pkgs/development/tools/parsing/alex/3.1.3.nix
similarity index 73%
rename from pkgs/development/tools/parsing/alex/3.1.2.nix
rename to pkgs/development/tools/parsing/alex/3.1.3.nix
index f969f9b6591..8174d851a31 100644
--- a/pkgs/development/tools/parsing/alex/3.1.2.nix
+++ b/pkgs/development/tools/parsing/alex/3.1.3.nix
@@ -1,13 +1,13 @@
-{ cabal, perl, QuickCheck }:
+{ cabal, happy, perl, QuickCheck }:
 
 cabal.mkDerivation (self: {
   pname = "alex";
-  version = "3.1.2";
-  sha256 = "0v8y6s9gwfk3cda6cpdl0n6vljmjbpnrdi3n93q41x24bhjyn50x";
+  version = "3.1.3";
+  sha256 = "14hajxpqb6va5mclp2k682bgw9sbmd372vw41kq5aq815bkschcd";
   isLibrary = false;
   isExecutable = true;
   buildDepends = [ QuickCheck ];
-  buildTools = [ perl ];
+  buildTools = [ happy perl ];
   meta = {
     homepage = "http://www.haskell.org/alex/";
     description = "Alex is a tool for generating lexical analysers in Haskell";
diff --git a/pkgs/top-level/haskell-packages.nix b/pkgs/top-level/haskell-packages.nix
index c7ddad8895d..57614893ba9 100644
--- a/pkgs/top-level/haskell-packages.nix
+++ b/pkgs/top-level/haskell-packages.nix
@@ -175,7 +175,7 @@ let result = let callPackage = x : y : modifyPrio (newScope result.finalReturn x
     xhtml        = self.xhtml_3000_2_1;
     zlib         = self.zlib_0_5_4_1;
     cabalInstall = self.cabalInstall_1_18_0_2;
-    alex         = self.alex_3_1_2;
+    alex         = self.alex_3_1_3;
     haddock      = self.haddock_2_13_2;
     happy        = self.happy_1_19_1;
     primitive    = self.primitive_0_5_1_0;      # semi-official, but specified
@@ -2462,8 +2462,8 @@ let result = let callPackage = x : y : modifyPrio (newScope result.finalReturn x
   alex_3_0_1 = callPackage ../development/tools/parsing/alex/3.0.1.nix {};
   alex_3_0_2 = callPackage ../development/tools/parsing/alex/3.0.2.nix {};
   alex_3_0_5 = callPackage ../development/tools/parsing/alex/3.0.5.nix {};
-  alex_3_1_2 = callPackage ../development/tools/parsing/alex/3.1.2.nix {};
-  alex = self.alex_3_1_2;
+  alex_3_1_3 = callPackage ../development/tools/parsing/alex/3.1.3.nix {};
+  alex = self.alex_3_1_3;
 
   alexMeta = callPackage ../development/tools/haskell/alex-meta {};