diff --git a/mongoose.h b/mongoose.h
index 28fe71b0..55a964d3 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -615,6 +615,7 @@ struct mg_mgr {
   struct mg_dns dns6;           // DNS for IPv6
   int dnstimeout;               // DNS resolve timeout in milliseconds
   unsigned long nextid;         // Next connection ID
+  void *userdata;               // Arbitrary user data pointer
 #if MG_ARCH == MG_ARCH_FREERTOS
   SocketSet_t ss;  // NOTE(lsm): referenced from socket struct
 #endif
diff --git a/src/net.h b/src/net.h
index 6f216699..2dba1367 100644
--- a/src/net.h
+++ b/src/net.h
@@ -23,6 +23,7 @@ struct mg_mgr {
   struct mg_dns dns6;           // DNS for IPv6
   int dnstimeout;               // DNS resolve timeout in milliseconds
   unsigned long nextid;         // Next connection ID
+  void *userdata;               // Arbitrary user data pointer
 #if MG_ARCH == MG_ARCH_FREERTOS
   SocketSet_t ss;  // NOTE(lsm): referenced from socket struct
 #endif