diff --git a/arch/arm/src/common/arm_createstack.c b/arch/arm/src/common/arm_createstack.c
index 1fb3c7abe1..9e39973906 100644
--- a/arch/arm/src/common/arm_createstack.c
+++ b/arch/arm/src/common/arm_createstack.c
@@ -151,7 +151,7 @@ int up_create_stack(struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
 
       if (!tcb->stack_alloc_ptr)
         {
-          serr("ERROR: Failed to allocate stack, size %d\n", stack_size);
+          serr("ERROR: Failed to allocate stack, size %zu\n", stack_size);
         }
 #endif
     }