diff --git a/sys/include/net/gcoap.h b/sys/include/net/gcoap.h
index ea47afd97287aabbc67101841f9b87bac27e8640..17bf14faa4df04654cbe58a4d9f618e9ddd8b29b 100644
--- a/sys/include/net/gcoap.h
+++ b/sys/include/net/gcoap.h
@@ -410,7 +410,8 @@ extern "C" {
  * @brief Stack size for module thread
  */
 #ifndef GCOAP_STACK_SIZE
-#define GCOAP_STACK_SIZE (THREAD_STACKSIZE_DEFAULT + DEBUG_EXTRA_STACKSIZE)
+#define GCOAP_STACK_SIZE (THREAD_STACKSIZE_DEFAULT + DEBUG_EXTRA_STACKSIZE \
+                          + sizeof(coap_pkt_t))
 #endif
 
 /**