diff --git a/rtl/unix/serial.pp b/rtl/unix/serial.pp
index 74f9005aaa..40c72668df 100644
--- a/rtl/unix/serial.pp
+++ b/rtl/unix/serial.pp
@@ -80,7 +80,7 @@ end;
 
 procedure SerFlush(Handle: TSerialHandle);
 begin
-  fsync(Handle);
+  fpfsync(Handle);
 end;
 
 function SerRead(Handle: TSerialHandle; var Buffer; Count: LongInt): LongInt;