diff --git a/portable/MemMang/heap_1.c b/portable/MemMang/heap_1.c
index a1e96bdf3..db7f94df7 100644
--- a/portable/MemMang/heap_1.c
+++ b/portable/MemMang/heap_1.c
@@ -94,7 +94,7 @@ void * pvPortMalloc( size_t xWantedSize )
         if( pucAlignedHeap == NULL )
         {
             /* Ensure the heap starts on a correctly aligned boundary. */
-            pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) & ucHeap[ portBYTE_ALIGNMENT ] ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
+            pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) & ucHeap[ portBYTE_ALIGNMENT - 1 ] ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
         }
 
         /* Check there is enough room left for the allocation and. */