diff --git a/netem/maketable.c b/netem/maketable.c
index ccb8f0c6..ad8620a4 100644
--- a/netem/maketable.c
+++ b/netem/maketable.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: NIST-PD */
 /*
  * Experimental data  distribution table generator
  * Taken from the uncopyrighted NISTnet code (public domain).
diff --git a/netem/normal.c b/netem/normal.c
index 90963f4e..5414be41 100644
--- a/netem/normal.c
+++ b/netem/normal.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: NIST-PD */
 /*
  * Normal distribution table generator
  * Taken from the uncopyrighted NISTnet code.
diff --git a/netem/pareto.c b/netem/pareto.c
index 51d9437d..5c802c90 100644
--- a/netem/pareto.c
+++ b/netem/pareto.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: NIST-PD */
 /*
  * Pareto distribution table generator
  * Taken from the uncopyrighted NISTnet code.
diff --git a/netem/paretonormal.c b/netem/paretonormal.c
index 9773e370..c36e325f 100644
--- a/netem/paretonormal.c
+++ b/netem/paretonormal.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: NIST-PD */
 /*
  * Paretoormal distribution table generator
  *
diff --git a/netem/stats.c b/netem/stats.c
index ed70f167..99c4feed 100644
--- a/netem/stats.c
+++ b/netem/stats.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: NIST-PD */
 /*
  * Experimental data  distribution table generator
  * Taken from the uncopyrighted NISTnet code (public domain).