diff --git a/inc/lektor/internal/os.h b/inc/lektor/internal/os.h
index 301fdd86517e540a92dac6f4fc05bb7e28e95c3c..d85395c61a96d3226c220637b8925220aa62ccb1 100644
--- a/inc/lektor/internal/os.h
+++ b/inc/lektor/internal/os.h
@@ -210,7 +210,7 @@ is_error_connection_aborted(int error)
 }
 
 PRIVATE_FUNCTION bool
-is_error_broken_pipe(int error)
+is_error_broken_pipe(int UNUSED error)
 {
 #if defined(LKT_OS_WIN) && (LKT_OS_WIN == 1)
     return false;