diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 7e97eb293..47c83bcc8 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -185,13 +185,15 @@ proc isCastable(dst, src: PType): bool =
   #  castableTypeKinds = {tyInt, tyPtr, tyRef, tyCstring, tyString, 
   #                       tySequence, tyPointer, tyNil, tyOpenArray,
   #                       tyProc, tySet, tyEnum, tyBool, tyChar}
+  if skipTypes(dst, abstractInst-{tyOpenArray}).kind == tyOpenArray:
+    return false
   var dstSize, srcSize: BiggestInt
 
   dstSize = computeSize(dst)
   srcSize = computeSize(src)
   if dstSize < 0: 
     result = false
-  elif srcSize < 0: 
+  elif srcSize < 0:
     result = false
   elif not typeAllowed(dst, skParam):
     result = false