diff --git a/src/edge_management.c b/src/edge_management.c
index 7381f1c..827a6b9 100644
--- a/src/edge_management.c
+++ b/src/edge_management.c
@@ -381,7 +381,7 @@ static void handleMgmtJson (mgmt_req_t *req, char *udp_buf, const int recvlen) {
     traceEvent(TRACE_DEBUG, "mgmt json %s", cmdlinebuf);
 
     /* we reuse the buffer already on the stack for all our strings */
-    STRBUF_INIT(buf, udp_buf);
+    STRBUF_INIT(buf, udp_buf, N2N_SN_PKTBUF_SIZE);
 
     mgmt_req_init2(req, buf, (char *)&cmdlinebuf);
 
@@ -476,7 +476,7 @@ void readFromMgmtSocket (n2n_edge_t *eee) {
 
     if((0 == memcmp(udp_buf, "help", 4)) || (0 == memcmp(udp_buf, "?", 1))) {
         strbuf_t *buf;
-        STRBUF_INIT(buf, &udp_buf);
+        STRBUF_INIT(buf, &udp_buf, sizeof(udp_buf));
         msg_len = snprintf(buf->str, buf->size,
                            "Help for edge management console:\n"
                            "\tstop    | Gracefully exit edge\n"
@@ -505,7 +505,7 @@ void readFromMgmtSocket (n2n_edge_t *eee) {
         traceEvent(TRACE_NORMAL, "+verb traceLevel=%u", (unsigned int) getTraceLevel());
 
         strbuf_t *buf;
-        STRBUF_INIT(buf, &udp_buf);
+        STRBUF_INIT(buf, &udp_buf, sizeof(udp_buf));
         msg_len = snprintf(buf->str, buf->size,
                            "> +OK traceLevel=%u\n", (unsigned int) getTraceLevel());
 
@@ -516,7 +516,7 @@ void readFromMgmtSocket (n2n_edge_t *eee) {
 
     if(0 == memcmp(udp_buf, "-verb", 5)) {
         strbuf_t *buf;
-        STRBUF_INIT(buf, &udp_buf);
+        STRBUF_INIT(buf, &udp_buf, sizeof(udp_buf));
 
         if(getTraceLevel() > 0) {
             setTraceLevel(getTraceLevel() - 1);
diff --git a/src/management.c b/src/management.c
index 70a3b4f..6f914b5 100644
--- a/src/management.c
+++ b/src/management.c
@@ -102,7 +102,7 @@ void mgmt_event_post2 (enum n2n_event_topic topic, int data0, void *data1, mgmt_
 
     char buf_space[100];
     strbuf_t *buf;
-    STRBUF_INIT(buf, buf_space);
+    STRBUF_INIT(buf, buf_space, sizeof(buf_space));
 
     char *tag;
     if(sub->type == N2N_MGMT_SUB) {
diff --git a/src/sn_management.c b/src/sn_management.c
index 4954cdf..5a288ca 100644
--- a/src/sn_management.c
+++ b/src/sn_management.c
@@ -240,7 +240,7 @@ static void handleMgmtJson (mgmt_req_t *req, char *udp_buf, const int recvlen) {
 
     /* we reuse the buffer already on the stack for all our strings */
     // xx
-    STRBUF_INIT(buf, udp_buf);
+    STRBUF_INIT(buf, udp_buf, N2N_SN_PKTBUF_SIZE);
 
     mgmt_req_init2(req, buf, (char *)&cmdlinebuf);
 
diff --git a/src/strbuf.h b/src/strbuf.h
index 1bf2c4b..cc2e7c2 100644
--- a/src/strbuf.h
+++ b/src/strbuf.h
@@ -14,10 +14,10 @@ typedef struct strbuf {
 } strbuf_t;
 
 // Initialise the strbuf pointer buf to point at the storage area p
-// p must be a known sized object
-#define STRBUF_INIT(buf,p) do { \
+// of size buflen
+#define STRBUF_INIT(buf,p,buflen) do { \
         buf = (void *)p; \
-        buf->size = sizeof(*p) - sizeof(size_t); \
+        buf->size = buflen - sizeof(size_t); \
 } while(0)