commit 28a6df1f7ad37df084192bcaa71156d9ef86d348
Author: Christoph Moench-Tegeder <cmt@burggraben.net>

    our asciidoc stack errors out on source blocks without language
    
    but a "listing" block without language style only results in
    warnings, so use that.

diff --git src/pcbnew/pcbnew_create_board.adoc src/pcbnew/pcbnew_create_board.adoc
index dddd7d3b..326fb3fe 100644
--- src/pcbnew/pcbnew_create_board.adoc
+++ src/pcbnew/pcbnew_create_board.adoc
@@ -787,7 +787,7 @@ Component classes can be referenced in <<custom-design-rules,custom design rules
 
 For example, to enforce a minimum clearance on all items belonging to footprints in the `Power_Stage` class:
 
-[source]
+[listing]
 ----
 (rule "Power component clearance"
     (condition "A.hasComponentClass('Power_Stage')")
@@ -797,7 +797,7 @@ For example, to enforce a minimum clearance on all items belonging to footprints
 
 To enforce courtyard clearance between two component classes:
 
-[source]
+[listing]
 ----
 (rule "Keep analog away from digital"
     (condition "A.hasComponentClass('Analog') && B.hasComponentClass('Digital')")