diff --git a/compiler/modulegraphs.nim b/compiler/modulegraphs.nim
index 55f751cda..b0b3e3f40 100644
--- a/compiler/modulegraphs.nim
+++ b/compiler/modulegraphs.nim
@@ -466,7 +466,11 @@ proc uniqueModuleName*(conf: ConfigRef; m: PSym): string =
   for i in 0..<trunc:
     let c = rel[i]
     case c
-    of 'a'..'z', '0'..'9':
+    of 'a'..'m':
+      result.add char(c.uint8 + 13)
+    of 'n'..'z':
+      result.add char(c.uint8 - 13)
+    of '0'..'9':
       result.add c
     of {os.DirSep, os.AltSep}:
       result.add 'Z' # because it looks a bit like '/'