diff --git a/doc/classes.texi b/doc/classes.texi
index ba8ef4c..e5bfe15 100644
--- a/doc/classes.texi
+++ b/doc/classes.texi
@@ -1309,7 +1309,7 @@ The subtype must implement at least the number of parameters declared in
   @itemize
   @item
   Each name in @var{params} must be a valid variable name, as satisfied by the
-  regular expression @code{/^[a-z][a-z0-9]*$/i}.
+  regular expression @code{/^[a-z_][a-z0-9_]*$/i}.
   @item
   The names are use purely for documentation and are not semantic.
   @end itemize
diff --git a/lib/util.js b/lib/util.js
index 5b6e5fb..7cb42d0 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -366,10 +366,10 @@ function verifyAbstractNames( name, params )
     var i = params.length;
     while ( i-- )
     {
-        if ( params[ i ].match( /^[a-z][a-z0-9]*$/i ) === null )
+        if ( params[ i ].match( /^[a-z_][a-z0-9_]*$/i ) === null )
         {
             throw SyntaxError(
-                "Member " + name + " contains invalid parameter: '" +
+                "Member " + name + " contains invalid parameter '" +
                 params[ i ] + "'"
             );
         }
diff --git a/test/test-util-prop-parse.js b/test/test-util-prop-parse.js
index 73009d2..2a9e975 100644
--- a/test/test-util-prop-parse.js
+++ b/test/test-util-prop-parse.js
@@ -205,7 +205,7 @@ assert.equal(
 
     assert.doesNotThrow( function()
     {
-        util.propParse( { 'abstract foo': [ 'valid' ] }, {} );
+        util.propParse( { 'abstract foo': [ 'valid_name' ] }, {} );
     }, SyntaxError, 'Valid var names as args should not throw exceptions' );
 } )();