diff --git a/mongoose.c b/mongoose.c
index baefd399..d27fb4cf 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -2687,7 +2687,8 @@ bool mg_aton(struct mg_str str, struct mg_addr *addr) {
 }
 
 struct mg_connection *mg_alloc_conn(struct mg_mgr *mgr) {
-  struct mg_connection *c = (struct mg_connection *) calloc(1, sizeof(*c));
+  struct mg_connection *c =
+      (struct mg_connection *) calloc(1, sizeof(*c) + mgr->extraconnsize);
   if (c != NULL) {
     c->mgr = mgr;
     c->id = ++mgr->nextid;
diff --git a/mongoose.h b/mongoose.h
index cc895b8d..2c1c882c 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -910,6 +910,7 @@ struct mg_mgr {
   void *active_dns_requests;    // DNS requests in progress
   struct mg_timer *timers;      // Active timers
   void *priv;                   // Used by the experimental stack
+  size_t extraconnsize;         // Used by the experimental stack
 #if MG_ARCH == MG_ARCH_FREERTOS_TCP
   SocketSet_t ss;  // NOTE(lsm): referenced from socket struct
 #endif
diff --git a/src/net.c b/src/net.c
index 93d81087..14fde456 100644
--- a/src/net.c
+++ b/src/net.c
@@ -139,7 +139,8 @@ bool mg_aton(struct mg_str str, struct mg_addr *addr) {
 }
 
 struct mg_connection *mg_alloc_conn(struct mg_mgr *mgr) {
-  struct mg_connection *c = (struct mg_connection *) calloc(1, sizeof(*c));
+  struct mg_connection *c =
+      (struct mg_connection *) calloc(1, sizeof(*c) + mgr->extraconnsize);
   if (c != NULL) {
     c->mgr = mgr;
     c->id = ++mgr->nextid;
diff --git a/src/net.h b/src/net.h
index e47bdfb0..88b64f2f 100644
--- a/src/net.h
+++ b/src/net.h
@@ -30,6 +30,7 @@ struct mg_mgr {
   void *active_dns_requests;    // DNS requests in progress
   struct mg_timer *timers;      // Active timers
   void *priv;                   // Used by the experimental stack
+  size_t extraconnsize;         // Used by the experimental stack
 #if MG_ARCH == MG_ARCH_FREERTOS_TCP
   SocketSet_t ss;  // NOTE(lsm): referenced from socket struct
 #endif