diff --git a/S32-setting-library/Exception.pod b/S32-setting-library/Exception.pod
index d1a905bfa..286d8f38f 100644
--- a/S32-setting-library/Exception.pod
+++ b/S32-setting-library/Exception.pod
@@ -768,6 +768,15 @@ Thrown when a backslash-variable is declared without initialization assignment.
         method message { "Term definition requires an initializer" }
     }
 
+=head3 X::Syntax::AddCategorial::MissingSeparator
+
+Thrown when a circumfix operator is defined without separator between opening and closing terminators.
+
+    my class X::Syntax::AddCategorial::MissingSeparator does X::Syntax {
+        has $.opname;
+        method message { "Unable to identify both starter and stopper from $.opname\nPerhaps you forgot to separate them with whitespace?" }
+    }
+
 =head3 X::Syntax::Signature::InvocantMarker
 
 Thrown when the invocant in a signature is anywhere else than after the