diff --git a/src/os.c b/src/os.c
index 2debc2a9..75895c1b 100644
--- a/src/os.c
+++ b/src/os.c
@@ -526,7 +526,7 @@ void* _mi_os_alloc_huge_os_pages(size_t pages, int numa_node, mi_msecs_t max_mse
     void* p = NULL;
     int err = _mi_prim_alloc_huge_os_pages(addr, MI_HUGE_OS_PAGE_SIZE, numa_node, &p);
     if (err != 0) {
-      _mi_warning_message("unable to allocate huge OS page (error: %d (0x%d), address: %p, size: %zx bytes)\n", err, err, addr, MI_HUGE_OS_PAGE_SIZE);
+      _mi_warning_message("unable to allocate huge OS page (error: %d (0x%x), address: %p, size: %zx bytes)\n", err, err, addr, MI_HUGE_OS_PAGE_SIZE);
       break;
     }
 
diff --git a/src/prim/unix/prim.c b/src/prim/unix/prim.c
index ebe54af6..189631f0 100644
--- a/src/prim/unix/prim.c
+++ b/src/prim/unix/prim.c
@@ -170,7 +170,7 @@ static void* unix_mmap_prim(void* addr, size_t size, size_t try_alignment, int p
       p = mmap(addr, size, protect_flags, flags | MAP_ALIGNED(n), fd, 0);
       if (p==MAP_FAILED || !_mi_is_aligned(p,try_alignment)) { 
         int err = errno;
-        _mi_warning_message("unable to directly request aligned OS memory (error: %d (0x%d), size: 0x%zx bytes, alignment: 0x%zx, hint address: %p)\n", err, err, size, try_alignment, hint);
+        _mi_warning_message("unable to directly request aligned OS memory (error: %d (0x%x), size: 0x%zx bytes, alignment: 0x%zx, hint address: %p)\n", err, err, size, try_alignment, hint);
       }
       if (p!=MAP_FAILED) return p;
       // fall back to regular mmap      
@@ -191,7 +191,7 @@ static void* unix_mmap_prim(void* addr, size_t size, size_t try_alignment, int p
       p = mmap(hint, size, protect_flags, flags, fd, 0);
       if (p==MAP_FAILED || !_mi_is_aligned(p,try_alignment)) { 
         int err = errno;
-        _mi_warning_message("unable to directly request hinted aligned OS memory (error: %d (0x%d), size: 0x%zx bytes, alignment: 0x%zx, hint address: %p)\n", err, err, size, try_alignment, hint);
+        _mi_warning_message("unable to directly request hinted aligned OS memory (error: %d (0x%x), size: 0x%zx bytes, alignment: 0x%zx, hint address: %p)\n", err, err, size, try_alignment, hint);
       }
       if (p!=MAP_FAILED) return p;
       // fall back to regular mmap