diff --git a/arch/sim/src/sim/sim_heap.c b/arch/sim/src/sim/sim_heap.c
index e95b559ff1..7b95441f7a 100644
--- a/arch/sim/src/sim/sim_heap.c
+++ b/arch/sim/src/sim/sim_heap.c
@@ -375,8 +375,7 @@ void *mm_realloc(struct mm_heap_s *heap, void *oldmem,
 
   if (size == 0)
     {
-      mm_free(heap, oldmem);
-      return NULL;
+      size = 1;
     }
 
   oldsize = host_mallocsize(oldmem);