diff --git a/doc/environments/groupthm/groupthm.dtx b/doc/environments/groupthm/groupthm.dtx
index 901b215..99cce66 100644
--- a/doc/environments/groupthm/groupthm.dtx
+++ b/doc/environments/groupthm/groupthm.dtx
@@ -1069,7 +1069,7 @@
     thmtools    .clist_set:N   = \l_@@_key_thmtools_clist,
     thmtools    .default:n     = {},
     unknown     .code:n        =
-      \msg_error:nnn { groupthm } { unknown ~ key } { \l_keys_key_str }
+      \msg_error:nnx { groupthm } { unknown ~ key } { \str_use:N \l_keys_key_str }
   }
 \keys_define:nn { groupthm / grouped ~ theorem }
   {
@@ -1082,7 +1082,7 @@
     starred ~ version       .bool_set:N    = \l_@@_key_starred_version_bool,
     starred ~ version       .default:n     = { true },
     unknown      .code:n        =
-      \msg_error:nnn { groupthm } { unknown ~ key } { \l_keys_key_str }
+      \msg_error:nnx { groupthm } { unknown ~ key } { \str_use:N \l_keys_key_str }
   }
 \keys_define:nn { groupthm / theorem ~ family }
   {
@@ -1095,14 +1095,14 @@
     starred ~ version       .bool_set:N    = \l_@@_key_starred_version_bool,
     starred ~ version       .default:n     = { true },
     unknown      .code:n        =
-      \msg_error:nnn { groupthm } { unknown ~ key } { \l_keys_key_str }
+      \msg_error:nnx { groupthm } { unknown ~ key } { \str_use:N \l_keys_key_str }
   }
 \keys_define:nn { groupthm / theorem ~ family ~ options }
   {
     starred ~ version       .bool_set:N    = \l_@@_key_starred_version_bool,
     starred ~ version       .default:n     = { true },
     unknown      .code:n        =
-      \msg_error:nnn { groupthm } { unknown ~ key } { \l_keys_key_str }
+      \msg_error:nnx { groupthm } { unknown ~ key } { \str_use:N \l_keys_key_str }
   }
 %    \end{macrocode}
 %