diff --git a/hatt.cabal b/hatt.cabal
--- a/hatt.cabal
+++ b/hatt.cabal
@@ -1,5 +1,5 @@
 Name:               hatt
-Version:            1.1
+Version:            1.1.1
 Stability:          experimental
 
 Synopsis:           A truth table generator for classical propositional logic.
diff --git a/src/Data/Logic/Propositional/Core.hs b/src/Data/Logic/Propositional/Core.hs
--- a/src/Data/Logic/Propositional/Core.hs
+++ b/src/Data/Logic/Propositional/Core.hs
@@ -41,7 +41,7 @@
 interpret (Negation      expr)      vs = not $ interpret expr vs
 interpret (Conjunction   exp1 exp2) vs = interpret exp1 vs && interpret exp2 vs
 interpret (Disjunction   exp1 exp2) vs = interpret exp1 vs || interpret exp2 vs
-interpret (Conditional   exp1 exp2) vs = not $ interpret exp1 vs || interpret exp2 vs
+interpret (Conditional   exp1 exp2) vs = not (interpret exp1 vs) || interpret exp2 vs
 interpret (Biconditional exp1 exp2) vs = interpret exp1 vs == interpret exp2 vs
 
 -- | Generates the possible assignments of variables in an expression.
diff --git a/src/Data/Logic/Propositional/Parser.hs b/src/Data/Logic/Propositional/Parser.hs
--- a/src/Data/Logic/Propositional/Parser.hs
+++ b/src/Data/Logic/Propositional/Parser.hs
@@ -73,5 +73,5 @@
     connective "<->" = Biconditional
     connective _     = error "Impossible case"
 
-variableChars :: [Char]
+variableChars :: String
 variableChars = ['a'..'z'] ++ ['A'..'Z']
diff --git a/src/hatt.hs b/src/hatt.hs
--- a/src/hatt.hs
+++ b/src/hatt.hs
@@ -27,7 +27,7 @@
                      &= help "Print the truth table for the given expression"
   , interactive = False &= help "Enter interactive mode"
   , pretty      = False &= help "Use Unicode logic symbols"
-  } &= summary "Hatt 1.0, (c) Benedict Eastaugh 2011"
+  } &= summary "Hatt 1.1.1, (c) Benedict Eastaugh 2011"
     &= program "hatt"
 
 main :: IO ()