diff --git a/lib/Makefile.am b/lib/Makefile.am
index f5852151..3b56ce4c 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -131,6 +131,7 @@ libshadow_la_SOURCES = \
 	shadowlog_internal.h \
 	shadowmem.c \
 	shell.c \
+	sizeof.h \
 	spawn.c \
 	sssd.c \
 	sssd.h \
diff --git a/lib/csrand.c b/lib/csrand.c
index e85eaa8a..9d6f1503 100644
--- a/lib/csrand.c
+++ b/lib/csrand.c
@@ -20,6 +20,7 @@
 #include "defines.h"
 #include "prototypes.h"
 #include "shadowlog.h"
+#include "sizeof.h"
 
 
 static uint32_t csrand_uniform32(uint32_t n);
diff --git a/lib/defines.h b/lib/defines.h
index a24a0c7d..d517424c 100644
--- a/lib/defines.h
+++ b/lib/defines.h
@@ -155,10 +155,6 @@
 #define SCALE DAY
 #endif
 
-#define WIDTHOF(x)   (sizeof(x) * CHAR_BIT)
-#define NITEMS(arr)  (sizeof((arr)) / sizeof((arr)[0]))
-#define STRLEN(s)    (NITEMS(s) - 1)
-
 /* Copy string pointed by B to array A with size checking.  It was originally
    in lmain.c but is _very_ useful elsewhere.  Some setuid root programs with
    very sloppy coding used to assume that BUFSIZ will always be enough...  */
diff --git a/lib/idmapping.c b/lib/idmapping.c
index b4e459e6..d9f9cd52 100644
--- a/lib/idmapping.c
+++ b/lib/idmapping.c
@@ -21,6 +21,7 @@
 #include <sys/capability.h>
 #endif
 #include "shadowlog.h"
+#include "sizeof.h"
 
 struct map_range *get_map_ranges(int ranges, int argc, char **argv)
 {
diff --git a/lib/sizeof.h b/lib/sizeof.h
new file mode 100644
index 00000000..b1a5daf1
--- /dev/null
+++ b/lib/sizeof.h
@@ -0,0 +1,21 @@
+/*
+ * SPDX-FileCopyrightText: 2022-2023, Alejandro Colomar <alx@kernel.org>
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+
+#ifndef SHADOW_INCLUDE_LIBMISC_SIZEOF_H_
+#define SHADOW_INCLUDE_LIBMISC_SIZEOF_H_
+
+
+#include <config.h>
+
+#include <limits.h>
+
+
+#define WIDTHOF(x)   (sizeof(x) * CHAR_BIT)
+#define NITEMS(arr)  (sizeof((arr)) / sizeof((arr)[0]))
+#define STRLEN(s)    (NITEMS(s) - 1)
+
+
+#endif  // include guard
diff --git a/lib/utmp.c b/lib/utmp.c
index 2cccdcd2..be8efa34 100644
--- a/lib/utmp.c
+++ b/lib/utmp.c
@@ -23,6 +23,7 @@
 #include <fcntl.h>
 
 #include "alloc.h"
+#include "sizeof.h"
 
 #ident "$Id$"
 
diff --git a/src/login_nopam.c b/src/login_nopam.c
index 4b0f6882..cd5bc5b7 100644
--- a/src/login_nopam.c
+++ b/src/login_nopam.c
@@ -56,6 +56,8 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>		/* for inet_ntoa() */
 
+#include "sizeof.h"
+
 #if !defined(MAXHOSTNAMELEN) || (MAXHOSTNAMELEN < 64)
 #undef MAXHOSTNAMELEN
 #define MAXHOSTNAMELEN 256