diff --git a/pkg/tinydtls/Makefile.include b/pkg/tinydtls/Makefile.include
index 1bcdeec1f9be..1c0fc197320a 100644
--- a/pkg/tinydtls/Makefile.include
+++ b/pkg/tinydtls/Makefile.include
@@ -63,6 +63,12 @@ endif
 PEER_MAX := $(or $(CONFIG_DTLS_PEER_MAX),$(patsubst -DCONFIG_DTLS_PEER_MAX=%,%,$(filter -DCONFIG_DTLS_PEER_MAX=%,$(CFLAGS))))
 ifneq (,$(PEER_MAX))
     CFLAGS += -DDTLS_PEER_MAX=$(PEER_MAX)
+else ifneq (,$(filter gcoap_dtls,$(USEMODULE)))
+    # The default value in sys/include/net/dtls.h for CONFIG_DTLS_PEER_MAX is 2
+    # when gcoap_dtls is active, otherwise 1. As the default in tinydtls is 1,
+    # we need to set it explicitly if the dtls.h default value deviates from
+    # the tinydtls default.
+    CFLAGS += -DDTLS_PEER_MAX=2
 endif
 
 HANDSHAKE_MAX := $(or $(CONFIG_DTLS_HANDSHAKE_MAX),$(patsubst -DCONFIG_DTLS_HANDSHAKE_MAX=%,%,$(filter -DCONFIG_DTLS_HANDSHAKE_MAX=%,$(CFLAGS))))