diff --git a/CMakeLists.txt b/CMakeLists.txt
index f025bb6..eb18c97 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,7 +12,6 @@ add_executable(netem main.c
 	utils.c
 	ts.c
 	tc.c
-	tcp.c
 	dist.c
 	dist-maketable.c
 )
diff --git a/probe.c b/probe.c
index 7dcda3c..798c25a 100644
--- a/probe.c
+++ b/probe.c
@@ -33,7 +33,6 @@
 #include "ts.h"
 #include "timing.h"
 #include "config.h"
-#include "tcp.h"
 #include "utils.h"
 #include "hist.h"
 
@@ -65,7 +64,7 @@ int probe_tcp(int sd, unsigned short dport, struct timespec *ts)
 	thdr.source = htons(sport);
 	thdr.dest = htons(dport);
 	thdr.doff = 5;
-	thdr.check = tcp_csum((unsigned short *) &thdr, sizeof(thdr));
+	thdr.check = chksum_rfc1071((unsigned short *) &thdr, sizeof(thdr));
 
 	msgh.msg_iov = &iov[1]; // only send TCP header
 	msgh.msg_iovlen = 1;
diff --git a/tcp.c b/tcp.c
deleted file mode 100644
index 6f1dbec..0000000
--- a/tcp.c
+++ /dev/null
@@ -1,18 +0,0 @@
-/** Userspace TCP functions.
- *
- * @author Steffen Vogel <post@steffenvogel.de>
- * @copyright 2014-2017, Steffen Vogel
- * @license GPLv3
- *********************************************************************************/
-
-unsigned short tcp_csum(unsigned short *buf, int len)
-{
-	unsigned long sum;
-
-	for(sum=0; len>0; len--)
-		sum += *buf++;
-	sum = (sum >> 16) + (sum &0xffff);
-	sum += (sum >> 16);
-
-	return (unsigned short)(~sum);
-}
\ No newline at end of file
diff --git a/tcp.h b/tcp.h
deleted file mode 100644
index 6a9ed31..0000000
--- a/tcp.h
+++ /dev/null
@@ -1,14 +0,0 @@
-/** Userspace TCP functions.
- *
- * @author Steffen Vogel <post@steffenvogel.de>
- * @copyright 2014-2017, Steffen Vogel 
- * @license GPLv3
- *********************************************************************************/
-
-#ifndef _TCP_H_
-#define _TCP_H_
-
-/** Simple checksum function, may use others such as Cyclic Redundancy Check, CRC */
-unsigned short tcp_csum(unsigned short *buf, int len);
-
-#endif
\ No newline at end of file