diff --git a/lib/Makefile.am b/lib/Makefile.am
index 0254977b..b5de79c5 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -37,6 +37,7 @@ libshadow_la_SOURCES = \
 	basename.c \
 	bit.c \
 	bit.h \
+	cast.h \
 	chkname.c \
 	chkname.h \
 	chowndir.c \
diff --git a/lib/cast.h b/lib/cast.h
new file mode 100644
index 00000000..9229528d
--- /dev/null
+++ b/lib/cast.h
@@ -0,0 +1,21 @@
+// SPDX-FileCopyrightText: 2022-2024, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#ifndef SHADOW_INCLUDE_LIB_CAST_H_
+#define SHADOW_INCLUDE_LIB_CAST_H_
+
+
+#include <config.h>
+
+#include "must_be.h"
+
+
+#define const_cast(T, p)                                                      \
+({                                                                            \
+	static_assert(is_same_type(typeof(&*(p)), const T), "");              \
+	(T) (p);                                                              \
+})
+
+
+#endif  // include guard