diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index 8727765add888390c4e85f9aa4962e9651b8334a..4c2e909a2d674f0e2c0183854200a008eef9c0c5 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -1,7 +1,9 @@
 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 /* Copyright (C) 2017-2018 Netronome Systems, Inc. */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
diff --git a/tools/bpf/bpftool/iter.c b/tools/bpf/bpftool/iter.c
index f88fdc820d23876f73f66b4f9dbe681700fd522a..a3e6b167153dbd347b44b4b2738304c4180b4a13 100644
--- a/tools/bpf/bpftool/iter.c
+++ b/tools/bpf/bpftool/iter.c
@@ -1,7 +1,9 @@
 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 // Copyright (C) 2020 Facebook
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <unistd.h>
 #include <linux/err.h>
 #include <bpf/libbpf.h>
diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c
index aaf99a0168c90b2636d474e1d46015d2c7bd487e..71cb258ab0eed3c51f75b20f6240c7ed5b5ea000 100644
--- a/tools/bpf/bpftool/jit_disasm.c
+++ b/tools/bpf/bpftool/jit_disasm.c
@@ -11,7 +11,9 @@
  * Licensed under the GNU General Public License, version 2.0 (GPLv2)
  */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <stdio.h>
 #include <stdarg.h>
 #include <stdint.h>
diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
index 526a332c48e6ebaaa2c9738d0e4fb05324ff19e3..c40e44c938ae6acaeb6e053f78b700e843519508 100644
--- a/tools/bpf/bpftool/net.c
+++ b/tools/bpf/bpftool/net.c
@@ -1,7 +1,9 @@
 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 // Copyright (C) 2018 Facebook
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <errno.h>
 #include <fcntl.h>
 #include <stdlib.h>
diff --git a/tools/bpf/bpftool/perf.c b/tools/bpf/bpftool/perf.c
index 226ec2c39052401c76fa78f1d6fa6150ec1b6104..91743445e4c7cdfebbbc13ad2a7737889a5d6a45 100644
--- a/tools/bpf/bpftool/perf.c
+++ b/tools/bpf/bpftool/perf.c
@@ -2,7 +2,9 @@
 // Copyright (C) 2018 Facebook
 // Author: Yonghong Song <yhs@fb.com>
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 10ec29cb45988cda5e1b938070ff5461b37579eb..dbf5489b8fde259bb33612c30f66ddd099e7a845 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -1,7 +1,9 @@
 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 /* Copyright (C) 2017-2018 Netronome Systems, Inc. */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <errno.h>
 #include <fcntl.h>
 #include <signal.h>
diff --git a/tools/bpf/bpftool/xlated_dumper.c b/tools/bpf/bpftool/xlated_dumper.c
index 2d9cd6a7b3c841616af8f66e464ae004a3b0cb4c..6fe3134ae45d4feaf72ac0fb2072deb8d68c844b 100644
--- a/tools/bpf/bpftool/xlated_dumper.c
+++ b/tools/bpf/bpftool/xlated_dumper.c
@@ -1,7 +1,9 @@
 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 /* Copyright (C) 2018 Netronome Systems, Inc. */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>