diff --git a/frontends/RainTypes.hs b/frontends/RainTypes.hs
index abe4322..9c54aca 100644
--- a/frontends/RainTypes.hs
+++ b/frontends/RainTypes.hs
@@ -101,9 +101,21 @@ checkExpressionTypes = everywhereASTM checkExpression
            trhs <- typeOfExpression rhs
            if (tlhs == trhs)
              then return e
-             else case (leastGeneralSharedTypeRain [tlhs,trhs]) of
-                    Nothing -> dieP m $ "Cannot find a suitable type to convert expression to, types are: " ++ show tlhs ++ " and " ++ show trhs
-                    Just t -> return $ A.Dyadic m op (convert t tlhs lhs) (convert t trhs rhs)
+             else if (isIntegerType tlhs && isIntegerType trhs) 
+                    then case (leastGeneralSharedTypeRain [tlhs,trhs]) of
+                           Nothing -> dieP m $ "Cannot find a suitable type to convert expression to, types are: " ++ show tlhs ++ " and " ++ show trhs
+                           Just t -> return $ A.Dyadic m op (convert t tlhs lhs) (convert t trhs rhs)
+                    else return e --TODO
+    checkExpression e@(A.Monadic m op rhs)
+      = do trhs <- typeOfExpression rhs
+           if (op == A.MonadicMinus)
+             then case trhs of
+                    A.Byte -> return $ A.Monadic m op $ convert A.Int16 trhs rhs
+                    A.UInt16 -> return $ A.Monadic m op $ convert A.Int32 trhs rhs
+                    A.UInt32 -> return $ A.Monadic m op $ convert A.Int64 trhs rhs
+                    A.UInt64 -> dieP m $ "Cannot apply unary minus to type: " ++ show trhs ++ " because there is no type large enough to safely contain the result"
+                    _ -> if (isIntegerType trhs) then return e else dieP m $ "Trying to apply unary minus to non-integer type: " ++ show trhs
+             else return e
     checkExpression e = return e
 
     convert :: A.Type -> A.Type -> A.Expression -> A.Expression
diff --git a/frontends/RainTypesTest.hs b/frontends/RainTypesTest.hs
index f9c95fa..412b0d5 100644
--- a/frontends/RainTypesTest.hs
+++ b/frontends/RainTypesTest.hs
@@ -103,6 +103,12 @@ checkExpressionTest = TestList
   ,pass 401 A.Int16 (Dy (Cast A.Int16 $ Var "x8") A.Plus (int A.Int16 200)) (Dy (Var "x8") A.Plus (int A.Int16 200))
   --This fails because you are trying to add a signed constant to an unsigned integer that cannot be expanded:
   ,fail 402 $ Dy (Var "xu64") A.Plus (int A.Int64 0)
+  
+  ,passSame 500 A.Int32 (Mon A.MonadicMinus (Var "x32"))
+  ,pass 501 A.Int32 (Mon A.MonadicMinus (Cast A.Int32 $ Var "xu16")) (Mon A.MonadicMinus (Var "xu16"))
+  ,fail 502 $ Mon A.MonadicMinus (Var "xu64")
+  ,pass 503 A.Int64 (Dy (Var "x") A.Plus (Cast A.Int64 $ Mon A.MonadicMinus (Var "x32"))) (Dy (Var "x") A.Plus (Mon A.MonadicMinus (Var "x32")))
+  
  ]
  where
   passSame :: Int -> A.Type -> ExprHelper -> Test
@@ -146,6 +152,7 @@ checkExpressionTest = TestList
              defVar "xu16" A.UInt16
              defVar "xu32" A.UInt32
              defVar "xu64" A.UInt64
+             defVar "x32" A.Int32
              defVar "x16" A.Int16
              defVar "x8" A.Int8