diff --git a/shared/nm-glib-aux/tests/test-shared-general.c b/shared/nm-glib-aux/tests/test-shared-general.c
index 3907bf8dd..d0fdedd51 100644
--- a/shared/nm-glib-aux/tests/test-shared-general.c
+++ b/shared/nm-glib-aux/tests/test-shared-general.c
@@ -798,7 +798,9 @@ test_nm_utils_get_next_realloc_size(void)
             }
 
             /* reserved_false is generally the next power of two - 24. */
-            if (!truncated_false) {
+            if (reserved_false == G_MAXSIZE)
+                g_assert_cmpuint(requested, >, G_MAXSIZE / 2u - 24u);
+            else if (!reserved_false) {
                 g_assert_cmpuint(reserved_false, <=, G_MAXSIZE - 24u);
                 if (reserved_false >= 40) {
                     const gsize _pow2 = reserved_false + 24u;
@@ -816,7 +818,9 @@ test_nm_utils_get_next_realloc_size(void)
             }
 
             /* reserved_true is generally the next 4k border - 24. */
-            if (!truncated_true) {
+            if (reserved_true == G_MAXSIZE)
+                g_assert_cmpuint(requested, >, G_MAXSIZE - 0x1000u - 24u);
+            else if (!truncated_true) {
                 g_assert_cmpuint(reserved_true, <=, G_MAXSIZE - 24u);
                 if (reserved_true > 8168u) {
                     const gsize page_border = reserved_true + 24u;
diff --git a/shared/nm-std-aux/nm-std-utils.c b/shared/nm-std-aux/nm-std-utils.c
index 9bf08e02a..8c7623715 100644
--- a/shared/nm-std-aux/nm-std-utils.c
+++ b/shared/nm-std-aux/nm-std-utils.c
@@ -65,16 +65,16 @@ nm_utils_get_next_realloc_size(bool true_realloc, size_t requested)
         return n - 24u;
     }
 
-    /* For large allocations (with !true_realloc) we allocate memory in chunks of
-     * 4K (- 24 bytes extra), assuming that the memory gets mmapped and thus
-     * realloc() is efficient by just reordering pages. */
-    n = ((requested + (0x0FFFu + 24u)) & ~((size_t) 0x0FFFu)) - 24u;
-
-    if (NM_UNLIKELY(n < requested)) {
+    if (NM_UNLIKELY(requested > SIZE_MAX - 0x1000u - 24u)) {
         /* overflow happened. */
         goto out_huge;
     }
 
+    /* For large allocations (with !true_realloc) we allocate memory in chunks of
+     * 4K (- 24 bytes extra), assuming that the memory gets mmapped and thus
+     * realloc() is efficient by just reordering pages. */
+    n = ((requested + (0x0FFFu + 24u)) & ~((size_t) 0x0FFFu)) - 24u;
+    nm_assert(n >= requested);
     return n;
 
 out_huge: