diff --git a/kernel/mem_domain.c b/kernel/mem_domain.c
index f3e6f6c74e120..e9ac6cff10992 100644
--- a/kernel/mem_domain.c
+++ b/kernel/mem_domain.c
@@ -155,6 +155,8 @@ void k_mem_domain_add_partition(struct k_mem_domain *domain,
 		}
 	}
 
+	__ASSERT((p_idx < arch_mem_domain_max_partitions_get()),
+		"no free partition slots available");
 	__ASSERT(p_idx < max_partitions,
 		 "no free partition slots available");
 
diff --git a/tests/kernel/mem_protect/mem_protect/src/mem_domain.c b/tests/kernel/mem_protect/mem_protect/src/mem_domain.c
index 2ca7ec3807c1f..72d212bc326c9 100644
--- a/tests/kernel/mem_protect/mem_protect/src/mem_domain.c
+++ b/tests/kernel/mem_protect/mem_protect/src/mem_domain.c
@@ -431,7 +431,10 @@ void test_mem_part_assert_add_overmax(void)
 	/* Add one more partition will trigger assert due to exceeding */
 	k_mem_domain_add_partition(&test_domain, &exceed_part);
 
-	/* should not reach here */
+	/* should not reach here but if it does clean up flag before
+	 * indicating failure
+	 */
+	need_recover_spinlock = false;
 	ztest_test_fail();
 }