diff --git a/README.md b/README.md
index 712d66e8..c1069ed4 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 [![Static Analysis](https://scan.coverity.com/projects/10970/badge.svg?flat=1)](https://scan.coverity.com/projects/obgm-libcoap)
 [![Fuzzing Status](https://oss-fuzz-build-logs.storage.googleapis.com/badges/libcoap.svg)](https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:libcoap)
 
-Copyright (C) 2010—2021 by Olaf Bergmann <bergmann@tzi.org> and others
+Copyright (C) 2010—2022 by Olaf Bergmann <bergmann@tzi.org> and others
 
 ABOUT LIBCOAP
 =============
@@ -38,6 +38,8 @@ The following RFCs are supported
 
 * RFC7252: The Constrained Application Protocol (CoAP)
 
+* RFC7390: Group Communication for the Constrained Application Protocol (CoAP)
+
 * RFC7641: Observing Resources in the Constrained Application Protocol (CoAP)
 
 * RFC7959: Block-Wise Transfers in the Constrained Application Protocol (CoAP)
diff --git a/doc/main.md b/doc/main.md
index fe36274c..dcd965d2 100644
--- a/doc/main.md
+++ b/doc/main.md
@@ -23,6 +23,8 @@ The following RFCs are supported
 
 * RFC7252: The Constrained Application Protocol (CoAP)
 
+* RFC7390: Group Communication for the Constrained Application Protocol (CoAP)
+
 * RFC7641: Observing Resources in the Constrained Application Protocol (CoAP)
 
 * RFC7959: Block-Wise Transfers in the Constrained Application Protocol (CoAP)
diff --git a/include/coap3/pdu.h b/include/coap3/pdu.h
index 9b18fb43..25b7bf4a 100644
--- a/include/coap3/pdu.h
+++ b/include/coap3/pdu.h
@@ -197,6 +197,9 @@ typedef enum coap_pdu_signaling_proto_t {
 #define COAP_MEDIATYPE_APPLICATION_CBOR          60 /* application/cbor  */
 #define COAP_MEDIATYPE_APPLICATION_CWT           61 /* application/cwt, RFC 8392  */
 
+/* Content formats from RFC 7390 */
+#define COAP_MEDIATYPE_APPLICATION_COAP_GROUP_JSON 256 /* application/coap-group+json */
+
 /* Content formats from RFC 8152 */
 #define COAP_MEDIATYPE_APPLICATION_COSE_SIGN     98 /* application/cose; cose-type="cose-sign"     */
 #define COAP_MEDIATYPE_APPLICATION_COSE_SIGN1    18 /* application/cose; cose-type="cose-sign1"    */
diff --git a/man/coap.txt.in b/man/coap.txt.in
index d109a875..6f424725 100644
--- a/man/coap.txt.in
+++ b/man/coap.txt.in
@@ -54,6 +54,8 @@ See
 
 "RFC7252: The Constrained Application Protocol (CoAP)"
 
+"RFC7390: Group Communication for the Constrained Application Protocol (CoAP)"
+
 "RFC7641: Observing Resources in the Constrained Application Protocol (CoAP)"
 
 "RFC7959: Block-Wise Transfers in the Constrained Application Protocol (CoAP)"
diff --git a/src/coap_debug.c b/src/coap_debug.c
index 1b9c922c..4da24006 100644
--- a/src/coap_debug.c
+++ b/src/coap_debug.c
@@ -459,6 +459,7 @@ print_content_format(unsigned int format_type,
     { COAP_MEDIATYPE_APPLICATION_SENSML_EXI, "application/sensml-exi" },
     { COAP_MEDIATYPE_APPLICATION_SENML_XML, "application/senml+xml" },
     { COAP_MEDIATYPE_APPLICATION_SENSML_XML, "application/sensml+xml" },
+    { COAP_MEDIATYPE_APPLICATION_COAP_GROUP_JSON, "application/coap-group+json" },
     { COAP_MEDIATYPE_APPLICATION_DOTS_CBOR, "application/dots+cbor" },
     { 75, "application/dcaf+cbor" }
   };