diff --git a/Makefile b/Makefile
index 4c34ee4..10f8737 100644
--- a/Makefile
+++ b/Makefile
@@ -12,7 +12,7 @@ SRCS=		calmwm.c screen.c xmalloc.c client.c menu.c \
 OBJS=		calmwm.o screen.o xmalloc.o client.o menu.o \
 		search.o util.o xutil.o conf.o xevents.o group.o \
 		kbfunc.o mousefunc.o strlcpy.o strlcat.o y.tab.o \
-		strtonum.o fgetln.o
+		strtonum.o fgetln.o reallocarray.o
 
 CPPFLAGS+=	`pkg-config --cflags fontconfig x11 xft xinerama xrandr`
 
diff --git a/calmwm.h b/calmwm.h
index 7652182..8baea11 100644
--- a/calmwm.h
+++ b/calmwm.h
@@ -28,6 +28,8 @@
 /* prototypes for portable-included functions */
 char *fgetln(FILE *, size_t *);
 long long strtonum(const char *, long long, long long, const char **);
+void *reallocarray(void *, size_t, size_t);
+
 
 #ifdef strlcat
 #define HAVE_STRLCAT
diff --git a/reallocarray.c b/reallocarray.c
new file mode 100644
index 0000000..ed3244e
--- /dev/null
+++ b/reallocarray.c
@@ -0,0 +1,38 @@
+/*	$OpenBSD: reallocarray.c,v 1.2 2014/12/08 03:45:00 bcook Exp $	*/
+/*
+ * Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+/*
+ * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
+ * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
+ */
+#define MUL_NO_OVERFLOW	((size_t)1 << (sizeof(size_t) * 4))
+
+void *
+reallocarray(void *optr, size_t nmemb, size_t size)
+{
+	if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+	    nmemb > 0 && SIZE_MAX / nmemb < size) {
+		errno = ENOMEM;
+		return NULL;
+	}
+	return realloc(optr, size * nmemb);
+}