diff --git a/sys/include/net/gcoap.h b/sys/include/net/gcoap.h
index ebac4e16d4264c071ed4d9b5cfee70f60ba3301c..df3045798fc2af65d2919cb7c97c3d1f6f3f9afb 100644
--- a/sys/include/net/gcoap.h
+++ b/sys/include/net/gcoap.h
@@ -209,6 +209,8 @@
 #ifndef NET_GCOAP_H
 #define NET_GCOAP_H
 
+#include <stdint.h>
+#include <stdatomic.h>
 #include "net/sock/udp.h"
 #include "nanocoap.h"
 #include "xtimer.h"
@@ -442,7 +444,7 @@ typedef struct {
                                         /**< Storage for open requests; if first
                                              byte of an entry is zero, the entry
                                              is available */
-    uint16_t last_message_id;           /**< Last message ID used */
+    atomic_uint next_message_id;        /**< Next message ID to use */
     sock_udp_ep_t observers[GCOAP_OBS_CLIENTS_MAX];
                                         /**< Observe clients; allows reuse for
                                              observe memos */
diff --git a/sys/net/application_layer/coap/gcoap.c b/sys/net/application_layer/coap/gcoap.c
index cd933dbe2cfad939fe12b7b4b9ade34f0954b96a..e615af2ecd01129d625dc55d323635baf24de9c3 100644
--- a/sys/net/application_layer/coap/gcoap.c
+++ b/sys/net/application_layer/coap/gcoap.c
@@ -590,7 +590,7 @@ kernel_pid_t gcoap_init(void)
     memset(&_coap_state.observers[0], 0, sizeof(_coap_state.observers));
     memset(&_coap_state.observe_memos[0], 0, sizeof(_coap_state.observe_memos));
     /* randomize initial value */
-    _coap_state.last_message_id = random_uint32() & 0xFFFF;
+    atomic_init(&_coap_state.next_message_id, (unsigned)random_uint32());
 
     return _pid;
 }
@@ -609,7 +609,6 @@ void gcoap_register_listener(gcoap_listener_t *listener)
 
 int gcoap_req_init(coap_pkt_t *pdu, uint8_t *buf, size_t len, unsigned code,
                                                               char *path) {
-    ssize_t hdrlen;
     (void)len;
 
     pdu->hdr = (coap_hdr_t *)buf;
@@ -624,11 +623,13 @@ int gcoap_req_init(coap_pkt_t *pdu, uint8_t *buf, size_t len, unsigned code,
                &rand,
                (GCOAP_TOKENLEN - i >= 4) ? 4 : GCOAP_TOKENLEN - i);
     }
-    hdrlen = coap_build_hdr(pdu->hdr, COAP_TYPE_NON, &token[0], GCOAP_TOKENLEN,
-                            code, ++_coap_state.last_message_id);
+    uint16_t msgid = (uint16_t)atomic_fetch_add(&_coap_state.next_message_id, 1);
+    ssize_t hdrlen = coap_build_hdr(pdu->hdr, COAP_TYPE_NON, &token[0], GCOAP_TOKENLEN,
+                                    code, msgid);
 #else
-    hdrlen = coap_build_hdr(pdu->hdr, COAP_TYPE_NON, NULL, GCOAP_TOKENLEN,
-                            code, ++_coap_state.last_message_id);
+    uint16_t msgid = (uint16_t)atomic_fetch_add(&_coap_state.next_message_id, 1);
+    ssize_t hdrlen = coap_build_hdr(pdu->hdr, COAP_TYPE_NON, NULL, GCOAP_TOKENLEN,
+                                    code, msgid);
 #endif
 
     if (hdrlen > 0) {
@@ -742,7 +743,6 @@ int gcoap_resp_init(coap_pkt_t *pdu, uint8_t *buf, size_t len, unsigned code)
 int gcoap_obs_init(coap_pkt_t *pdu, uint8_t *buf, size_t len,
                                                   const coap_resource_t *resource)
 {
-    ssize_t hdrlen;
     gcoap_observe_memo_t *memo = NULL;
 
     _find_obs_memo_resource(&memo, resource);
@@ -751,10 +751,11 @@ int gcoap_obs_init(coap_pkt_t *pdu, uint8_t *buf, size_t len,
         return GCOAP_OBS_INIT_UNUSED;
     }
 
-    pdu->hdr = (coap_hdr_t *)buf;
-    hdrlen   = coap_build_hdr(pdu->hdr, COAP_TYPE_NON, &memo->token[0],
-                              memo->token_len, COAP_CODE_CONTENT,
-                              ++_coap_state.last_message_id);
+    pdu->hdr       = (coap_hdr_t *)buf;
+    uint16_t msgid = (uint16_t)atomic_fetch_add(&_coap_state.next_message_id, 1);
+    ssize_t hdrlen = coap_build_hdr(pdu->hdr, COAP_TYPE_NON, &memo->token[0],
+                                    memo->token_len, COAP_CODE_CONTENT, msgid);
+
     if (hdrlen > 0) {
         uint32_t now       = xtimer_now_usec();
         pdu->observe_value = (now >> GCOAP_OBS_TICK_EXPONENT) & 0xFFFFFF;