diff --git a/lkql_checker/doc/gnatcheck_rm/using_gnatcheck.rst b/lkql_checker/doc/gnatcheck_rm/using_gnatcheck.rst
index 34a052f02..955823d78 100644
--- a/lkql_checker/doc/gnatcheck_rm/using_gnatcheck.rst
+++ b/lkql_checker/doc/gnatcheck_rm/using_gnatcheck.rst
@@ -515,6 +515,12 @@ to simplify mapping your coding standard requirements onto
     ...
     bar.ads:17:3: this is not good [My_Coding_Rule_N|Gnatcheck_Rule_N]
 
+.. attention::
+
+  A custom coding rule name can be any sequence of non-whitespace characters.
+  Moreover, the ":" (colon) character is forbidden in those names for parsing
+  purposes.
+
 .. _gnatcheck_Exit_Codes:
 
 GNATcheck Exit Codes
diff --git a/lkql_checker/src/gnatcheck-diagnoses.adb b/lkql_checker/src/gnatcheck-diagnoses.adb
index b1df4a959..b8af920c5 100644
--- a/lkql_checker/src/gnatcheck-diagnoses.adb
+++ b/lkql_checker/src/gnatcheck-diagnoses.adb
@@ -44,7 +44,7 @@ package body Gnatcheck.Diagnoses is
    --  Matcher for a diagnostic
 
    Match_Rule_Name : constant Pattern_Matcher :=
-     Compile ("^""(\w+)\s*(?::\s*(.*))?""$");
+     Compile ("^""([^\s:]+)\s*(?::\s*(.*))?""$");
    --  Matcher for a rule name and potential arguments
 
    Match_Rule_Param : constant Pattern_Matcher :=