diff --git a/common/Types.hs b/common/Types.hs
index 74a0bbb..f813fa5 100644
--- a/common/Types.hs
+++ b/common/Types.hs
@@ -20,7 +20,7 @@ with this program.  If not, see <http://www.gnu.org/licenses/>.
 module Types
   (
     specTypeOfName, abbrevModeOfName, typeOfName, typeOfExpression, typeOfVariable, underlyingType, stripArrayType, abbrevModeOfVariable, abbrevModeOfSpec
-    , isRealType, isIntegerType, isCaseableType, resolveUserType, isSafeConversion, isPreciseConversion
+    , isRealType, isIntegerType, isCaseableType, resolveUserType, isSafeConversion, isPreciseConversion, isImplicitConversionRain
     , returnTypesOfFunction
     , BytesInResult(..), bytesInType, sizeOfReplicator, sizeOfStructured
 
@@ -328,6 +328,16 @@ findMeta e = if null metaList then emptyMeta else head metaList
     findMeta' :: Meta -> Meta
     findMeta' m = m
 
+-- | Checks whether a given conversion can be done implicitly in Rain
+-- Parameters are src dest
+isImplicitConversionRain :: A.Type -> A.Type -> Bool
+isImplicitConversionRain x y
+  = if (x == y)
+      then True
+      else if (x == A.Bool || y == A.Bool)
+             then False
+             else isSafeConversion x y
+
 -- | Is a conversion between two types precise (i.e. do you need to specify
 -- ROUND or TRUNC when doing it)?
 isPreciseConversion :: A.Type -> A.Type -> Bool
diff --git a/frontends/RainPasses.hs b/frontends/RainPasses.hs
index b184bd2..0e537ac 100644
--- a/frontends/RainPasses.hs
+++ b/frontends/RainPasses.hs
@@ -198,7 +198,7 @@ matchParamPass = everywhereM ((mkM matchParamPassProc) `extM` matchParamPassFunc
     --Adds a cast between two types if it is safe to do so, otherwise gives an error
     doCast :: Int -> A.Type -> A.Type -> A.Expression -> PassM A.Expression
     doCast index to from item
-      = if isSafeConversion from to
+      = if isImplicitConversionRain from to
           then return $ A.Conversion (findMeta item) A.DefaultConversion to item
           else dieP (findMeta item) $ "Could not perform implicit cast from supplied type: " ++ (show from) ++
             " to expected type: " ++ (show to) ++ " for parameter (zero-based): " ++ (show index)