diff --git a/lib/pure/ospaths.nim b/lib/pure/ospaths.nim
index 9fc816f2f5..65588529e0 100644
--- a/lib/pure/ospaths.nim
+++ b/lib/pure/ospaths.nim
@@ -10,7 +10,7 @@
 # Included by the ``os`` module but a module in its own right for NimScript
 # support.
 
-when isMainModule:
+when not declared(os):
   {.pragma: rtl.}
   import strutils