diff --git a/src/core/config/openthread-core-default-config.h b/src/core/config/openthread-core-default-config.h
index 75c76a2d5..25053c649 100644
--- a/src/core/config/openthread-core-default-config.h
+++ b/src/core/config/openthread-core-default-config.h
@@ -270,7 +270,7 @@
 #if OPENTHREAD_CONFIG_COAP_SECURE_API_ENABLE
 #define OPENTHREAD_CONFIG_HEAP_INTERNAL_SIZE (3072 * sizeof(void *))
 #else
-#define OPENTHREAD_CONFIG_HEAP_INTERNAL_SIZE (1536 * sizeof(void *))
+#define OPENTHREAD_CONFIG_HEAP_INTERNAL_SIZE (1568 * sizeof(void *))
 #endif
 #endif