diff --git a/slirp/src/debug.h b/slirp/src/debug.h
index 44d922df37..2e503ad7fa 100644
--- a/slirp/src/debug.h
+++ b/slirp/src/debug.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/if.c b/slirp/src/if.c
index 1830cc396c..b8cddebf66 100644
--- a/slirp/src/if.c
+++ b/slirp/src/if.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/if.h b/slirp/src/if.h
index 69569c10df..8a60c4e052 100644
--- a/slirp/src/if.h
+++ b/slirp/src/if.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/main.h b/slirp/src/main.h
index f11d4572b7..a88774215f 100644
--- a/slirp/src/main.h
+++ b/slirp/src/main.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/mbuf.c b/slirp/src/mbuf.c
index 521c02c967..f079a86d78 100644
--- a/slirp/src/mbuf.c
+++ b/slirp/src/mbuf.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski
  *
diff --git a/slirp/src/misc.c b/slirp/src/misc.c
index 937a418d4e..da41f3bb5f 100644
--- a/slirp/src/misc.c
+++ b/slirp/src/misc.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/misc.h b/slirp/src/misc.h
index c2ceadb591..4eaa2466d7 100644
--- a/slirp/src/misc.h
+++ b/slirp/src/misc.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/sbuf.c b/slirp/src/sbuf.c
index 51a9f0cc7d..815823ffbe 100644
--- a/slirp/src/sbuf.c
+++ b/slirp/src/sbuf.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/sbuf.h b/slirp/src/sbuf.h
index 1cb9a42834..ece616e317 100644
--- a/slirp/src/sbuf.h
+++ b/slirp/src/sbuf.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/socket.c b/slirp/src/socket.c
index f2428a3ae8..ad58262a06 100644
--- a/slirp/src/socket.c
+++ b/slirp/src/socket.c
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *
diff --git a/slirp/src/socket.h b/slirp/src/socket.h
index e4d12cd591..10a0c78a26 100644
--- a/slirp/src/socket.h
+++ b/slirp/src/socket.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 1995 Danny Gasparovski.
  *