diff --git a/sys/net/application_layer/gcoap/Makefile.include b/sys/net/application_layer/gcoap/Makefile.include
index 5be3bbb663..4cb403e57c 100644
--- a/sys/net/application_layer/gcoap/Makefile.include
+++ b/sys/net/application_layer/gcoap/Makefile.include
@@ -2,3 +2,6 @@ ifeq (2, $(words $(filter ipv4 ipv6, $(USEMODULE))))
   $(shell $(COLOR_ECHO) "$(COLOR_YELLOW)Due to limitations in the gcoap API it is currently not \
                          possible to use a dual stack setup$(COLOR_RESET)" 1>&2)
 endif
+
+CONFIG_GCOAP_PDU_BUF_SIZE := $(or $(CONFIG_GCOAP_PDU_BUF_SIZE),128)
+DTLS_MAX_BUF ?= ($(CONFIG_GCOAP_PDU_BUF_SIZE) + 36)