diff --git a/portable/MemMang/heap_4.c b/portable/MemMang/heap_4.c
index 50af15dfb..738ff750d 100644
--- a/portable/MemMang/heap_4.c
+++ b/portable/MemMang/heap_4.c
@@ -508,7 +508,8 @@ static void prvInsertBlockIntoFreeList( BlockLink_t * pxBlockToInsert ) /* PRIVI
 
     /* Iterate through the list until a block is found that has a higher address
      * than the block being inserted. */
-    for( pxIterator = &xStart; heapPROTECT_BLOCK_POINTER( pxIterator->pxNextFreeBlock ) < pxBlockToInsert; pxIterator = heapPROTECT_BLOCK_POINTER( pxIterator->pxNextFreeBlock ) )
+    for( pxIterator = &xStart; ( portPOINTER_SIZE_TYPE ) heapPROTECT_BLOCK_POINTER( pxIterator->pxNextFreeBlock ) < ( portPOINTER_SIZE_TYPE ) pxBlockToInsert;
+         pxIterator = heapPROTECT_BLOCK_POINTER( pxIterator->pxNextFreeBlock ) )
     {
         /* Nothing to do here, just iterate to the right position. */
     }