diff --git a/tests/kernel/mbox/mbox_api/src/test_mbox_api.c b/tests/kernel/mbox/mbox_api/src/test_mbox_api.c
index 64d426f9ab2..0ad25e9600f 100644
--- a/tests/kernel/mbox/mbox_api/src/test_mbox_api.c
+++ b/tests/kernel/mbox/mbox_api/src/test_mbox_api.c
@@ -7,7 +7,11 @@
 #include <ztest.h>
 
 #define TIMEOUT 100
+#if !defined(CONFIG_BOARD_QEMU_X86)
 #define STACK_SIZE (512 + CONFIG_TEST_EXTRA_STACKSIZE)
+#else
+#define STACK_SIZE (640 + CONFIG_TEST_EXTRA_STACKSIZE)
+#endif
 #define MAIL_LEN 64
 
 /**TESTPOINT: init via K_MBOX_DEFINE*/
diff --git a/tests/kernel/sleep/src/main.c b/tests/kernel/sleep/src/main.c
index 9b09c71376f..d6560fe41a9 100644
--- a/tests/kernel/sleep/src/main.c
+++ b/tests/kernel/sleep/src/main.c
@@ -24,9 +24,9 @@
 #include <stdbool.h>
 
 #if defined(CONFIG_ASSERT) && defined(CONFIG_DEBUG)
-#define THREAD_STACK    (384 + CONFIG_TEST_EXTRA_STACKSIZE)
+#define THREAD_STACK    (512 + CONFIG_TEST_EXTRA_STACKSIZE)
 #else
-#define THREAD_STACK    (256 + CONFIG_TEST_EXTRA_STACKSIZE)
+#define THREAD_STACK    (384 + CONFIG_TEST_EXTRA_STACKSIZE)
 #endif
 
 #define TEST_THREAD_PRIORITY	-4
diff --git a/tests/kernel/threads/lifecycle/lifecycle_api/src/test_threads_set_priority.c b/tests/kernel/threads/lifecycle/lifecycle_api/src/test_threads_set_priority.c
index 96eba58f02b..f0042e8085d 100644
--- a/tests/kernel/threads/lifecycle/lifecycle_api/src/test_threads_set_priority.c
+++ b/tests/kernel/threads/lifecycle/lifecycle_api/src/test_threads_set_priority.c
@@ -6,7 +6,7 @@
 
 #include <ztest.h>
 
-#define STACK_SIZE (256 + CONFIG_TEST_EXTRA_STACKSIZE)
+#define STACK_SIZE (384 + CONFIG_TEST_EXTRA_STACKSIZE)
 K_THREAD_STACK_EXTERN(tstack);
 extern struct k_thread tdata;
 static int thread2_data;
diff --git a/tests/kernel/threads/scheduling/schedule_api/src/test_sched.h b/tests/kernel/threads/scheduling/schedule_api/src/test_sched.h
index 695481cfdab..10ea8db9d35 100644
--- a/tests/kernel/threads/scheduling/schedule_api/src/test_sched.h
+++ b/tests/kernel/threads/scheduling/schedule_api/src/test_sched.h
@@ -10,7 +10,7 @@
 #include <zephyr.h>
 #include <ztest.h>
 
-#if defined(CONFIG_RISCV32)
+#if defined(CONFIG_RISCV32) || defined(CONFIG_X86)
 #define STACK_SIZE 512
 #else
 #define STACK_SIZE (256 + CONFIG_TEST_EXTRA_STACKSIZE)