diff --git a/flake.nix b/flake.nix
index 6fabe7d657..91cf43d0fe 100644
--- a/flake.nix
+++ b/flake.nix
@@ -385,6 +385,7 @@
                   "chat_send_cmd"
                   "chat_send_remote_cmd"
                   "chat_valid_name"
+                  "chat_json_length"
                   "chat_write_file"
                 ];
                 postInstall = ''
@@ -487,6 +488,7 @@
                   "chat_send_cmd"
                   "chat_send_remote_cmd"
                   "chat_valid_name"
+                  "chat_json_length"
                   "chat_write_file"
                 ];
                 postInstall = ''
diff --git a/libsimplex.dll.def b/libsimplex.dll.def
index f927e3ee24..592e6db4f2 100644
--- a/libsimplex.dll.def
+++ b/libsimplex.dll.def
@@ -12,6 +12,7 @@ EXPORTS
     chat_parse_server
     chat_password_hash
     chat_valid_name
+    chat_json_length
     chat_encrypt_media
     chat_decrypt_media
     chat_write_file