diff --git a/backends/BackendPasses.hs b/backends/BackendPasses.hs
index c23eb8a..46dd6af 100644
--- a/backends/BackendPasses.hs
+++ b/backends/BackendPasses.hs
@@ -135,15 +135,19 @@ declareSizesArray = doGeneric `ext1M` doStructured
                0 -> return $ makeStaticSizeSpec m n_sizes
                                [if d == A.UnknownDimension then A.Dimension (bytes `div` (knownDimsTotal * biElem)) else d | d <- ds]
                _ -> dieP m "RETYPES has sizes that do not fit"
+             -- TODO apply a dynamic check for this part:
              BIUnknown -> dieP m $ "Cannot handle RETYPES sizes: " ++ show birhs
                -- Some array dimensions are not known at compile-time:
-             _ ->  do let A.Array _ elemSrcT = t
+             _ ->  do let A.Array srcDs elemSrcT = t
                       BIJust biSrcElem <- bytesInType elemSrcT
+                      let A.Variable _ srcN = v
+                          multipliedDimsV = foldl (A.Dyadic m A.Mul) (makeConstant m biSrcElem)
+                            [A.ExprVariable m $ A.SubscriptedVariable m (A.Subscript m $ makeConstant m i) (A.Variable m $ append_sizes srcN)  | i <- [0 .. length srcDs - 1]]
                       return $ makeDynamicSizeSpec m n_sizes
                             [case d of
                                -- TODO add a run-time check here for invalid retypes
-                               A.UnknownDimension -> (A.Dyadic m A.Div (A.Dyadic m A.Mul (makeConstant m biSrcElem) (A.SizeVariable m v))
-                                 (makeConstant m $ knownDimsTotal * biElem))
+                               A.UnknownDimension -> A.Dyadic m A.Div multipliedDimsV
+                                 (makeConstant m $ knownDimsTotal * biElem)
                                A.Dimension n -> makeConstant m n
                             | d <- ds]
            defineSizesName m n_sizes sizeSpecType
diff --git a/backends/GenerateC.hs b/backends/GenerateC.hs
index 2e17b46..0bd0260 100644
--- a/backends/GenerateC.hs
+++ b/backends/GenerateC.hs
@@ -766,6 +766,10 @@ cgenArraySubscript checkValid v es
         gen = sequence_ $ intersperse (tell ["*"]) $ genSub : genChunks
         genSub
             = if checkValid
+                 -- Total, complete and utter horrible hack until we have
+                 -- some way of expressing unchecked subscripting in the AST:
+                 -- TODO fix this
+                 && (not $ "_sizes" `isSuffixOf` (let A.Variable _ (A.Name _ _ n) = v in n))
                 then do tell ["occam_check_index("]
                         call genExpression e
                         tell [","]