diff --git a/driver/opae/vlsim/opae_sim.cpp b/driver/opae/vlsim/opae_sim.cpp
index dd5a84c1..0844ee17 100644
--- a/driver/opae/vlsim/opae_sim.cpp
+++ b/driver/opae/vlsim/opae_sim.cpp
@@ -66,7 +66,7 @@ static void *__aligned_malloc(size_t alignment, size_t size) {
   // reserve margin for alignment and storing of unaligned address
   size_t margin = (alignment-1) + sizeof(void*);
   void *unaligned_addr = malloc(size + margin);
-  void **aligned_addr = (void**)((uintptr_t)(unaligned_addr + margin) & ~(alignment-1));
+  void **aligned_addr = (void**)((uintptr_t)(((uint8_t*)unaligned_addr) + margin) & ~(alignment-1));
   aligned_addr[-1] = unaligned_addr;
   return aligned_addr;
 }
diff --git a/runtime/src/vx_spawn.c b/runtime/src/vx_spawn.c
index e3b68a19..0fc8184d 100644
--- a/runtime/src/vx_spawn.c
+++ b/runtime/src/vx_spawn.c
@@ -118,7 +118,7 @@ void vx_spawn_tasks(int num_tasks, pfn_callback callback , const void * args) {
   //--
 	if (nW >= 1)	{ 
     int nw = MIN(nW, NW);    
-	  vx_wspawn(nw, (unsigned)&spawn_tasks_callback);
+	  vx_wspawn(nw, spawn_tasks_callback);
     spawn_tasks_callback();
 	}  
 
@@ -247,7 +247,7 @@ void vx_spawn_kernel(struct context_t * ctx, pfn_workgroup_func wg_func, const v
   //--
 	if (nW >= 1)	{ 
     int nw = MIN(nW, NW);    
-	  vx_wspawn(nw, (unsigned)&spawn_kernel_callback);
+	  vx_wspawn(nw, spawn_kernel_callback);
     spawn_kernel_callback();
 	}