Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php (revision 18607)
+++ wp-includes/functions.php (working copy)
@@ -3524,8 +3524,16 @@
 
 	// Allow plugin to filter the output error trigger
 	if ( WP_DEBUG && apply_filters( 'doing_it_wrong_trigger_error', true ) ) {
+		$backtrace = debug_backtrace();
+		if ( isset( $backtrace[1]['line'] ) )
+			$source = sprintf( __( '(Source: %1$s line %2$s)' ), $backtrace[1]['file'], $backtrace[1]['line'] );
+		else if ( isset( $backtrace[1]['class'] ) )
+			$source = sprintf( __( '(Source: %1$s%2$s%3$s)' ), $backtrace[1]['class'], $backtrace[1]['type'], $backtrace[1]['function'] );
+		else
+			$source = __( '(Source: unknown)' );
+
 		$version = is_null( $version ) ? '' : sprintf( __( '(This message was added in version %s.)' ), $version );
-		trigger_error( sprintf( __( '%1$s was called <strong>incorrectly</strong>. %2$s %3$s' ), $function, $message, $version ) );
+		trigger_error( sprintf( __( '%1$s was called <strong>incorrectly</strong>. %2$s %3$s %4$s' ), $function, $message, $source, $version ) );
 	}
 }