diff --git a/lib/pure/pegs.nim b/lib/pure/pegs.nim
index 61a1c08c79..240ea0945c 100644
--- a/lib/pure/pegs.nim
+++ b/lib/pure/pegs.nim
@@ -1742,7 +1742,8 @@ when isMainModule:
   else:
     assert false
 
-  var matches: array[0..maxSubpatterns-1, string]
+  when not definedInScope(matches):
+    var matches: array[0..maxSubpatterns-1, string]
   if match("abcdefg", peg"c {d} ef {g}", matches, 2):
     assert matches[0] == "d"
     assert matches[1] == "g"