diff --git a/serialport.c b/serialport.c
index 781fbde..c53a639 100644
--- a/serialport.c
+++ b/serialport.c
@@ -563,5 +563,7 @@ void sp_free_error_message(char *message)
 {
 #ifdef _WIN32
 	LocalFree(message);
+#else
+	(void)message;
 #endif
 }