diff --git a/examples/platforms/cc2538/startup-gcc.c b/examples/platforms/cc2538/startup-gcc.c
index a56768f16..ba6e55a07 100644
--- a/examples/platforms/cc2538/startup-gcc.c
+++ b/examples/platforms/cc2538/startup-gcc.c
@@ -59,7 +59,7 @@ extern void RFCoreRxTxIntHandler(void);
 extern void RFCoreErrIntHandler(void);
 extern void main(void);
 
-static uint64_t stack[256] __attribute__((section(".stack")));
+static uint64_t stack[384] __attribute__((section(".stack")));
 
 __attribute__((section(".vectors"), used))
 void (*const vectors[])(void) =
diff --git a/src/core/openthread-core-default-config.h b/src/core/openthread-core-default-config.h
index e41f3b6c4..b69ce15d3 100644
--- a/src/core/openthread-core-default-config.h
+++ b/src/core/openthread-core-default-config.h
@@ -42,7 +42,7 @@
  *
  */
 #ifndef OPENTHREAD_CONFIG_NUM_MESSAGE_BUFFERS
-#define OPENTHREAD_CONFIG_NUM_MESSAGE_BUFFERS               64
+#define OPENTHREAD_CONFIG_NUM_MESSAGE_BUFFERS               48
 #endif  // OPENTHREAD_CONFIG_NUM_MESSAGE_BUFFERS
 
 /**