diff --git a/grub-core/kern/mm.c b/grub-core/kern/mm.c
index d54f3f240..ee4d58d81 100644
--- a/grub-core/kern/mm.c
+++ b/grub-core/kern/mm.c
@@ -515,7 +515,7 @@ grub_debug_malloc (const char *file, int line, grub_size_t size)
   void *ptr;
 
   if (grub_mm_debug)
-    grub_printf ("%s:%d: malloc (0x%zx) = ", file, line, size);
+    grub_printf ("%s:%d: malloc (0x%" PRIxGRUB_SIZE ") = ", file, line, size);
   ptr = grub_malloc (size);
   if (grub_mm_debug)
     grub_printf ("%p\n", ptr);
@@ -528,7 +528,7 @@ grub_debug_zalloc (const char *file, int line, grub_size_t size)
   void *ptr;
 
   if (grub_mm_debug)
-    grub_printf ("%s:%d: zalloc (0x%zx) = ", file, line, size);
+    grub_printf ("%s:%d: zalloc (0x%" PRIxGRUB_SIZE ") = ", file, line, size);
   ptr = grub_zalloc (size);
   if (grub_mm_debug)
     grub_printf ("%p\n", ptr);
@@ -547,7 +547,7 @@ void *
 grub_debug_realloc (const char *file, int line, void *ptr, grub_size_t size)
 {
   if (grub_mm_debug)
-    grub_printf ("%s:%d: realloc (%p, 0x%zx) = ", file, line, ptr, size);
+    grub_printf ("%s:%d: realloc (%p, 0x%" PRIxGRUB_SIZE ") = ", file, line, ptr, size);
   ptr = grub_realloc (ptr, size);
   if (grub_mm_debug)
     grub_printf ("%p\n", ptr);
@@ -561,8 +561,8 @@ grub_debug_memalign (const char *file, int line, grub_size_t align,
   void *ptr;
 
   if (grub_mm_debug)
-    grub_printf ("%s:%d: memalign (0x%zx, 0x%zx) = ",
-		 file, line, align, size);
+    grub_printf ("%s:%d: memalign (0x%" PRIxGRUB_SIZE  ", 0x%" PRIxGRUB_SIZE  
+		 ") = ", file, line, align, size);
   ptr = grub_memalign (align, size);
   if (grub_mm_debug)
     grub_printf ("%p\n", ptr);