diff --git a/Makefile b/Makefile
index 6d2929f..6be898f 100644
--- a/Makefile
+++ b/Makefile
@@ -17,6 +17,7 @@ OBJS=		calmwm.o screen.o xmalloc.o client.o menu.o \
 CPPFLAGS+=	`pkg-config --cflags fontconfig x11 xft xinerama xrandr`
 
 CFLAGS?=	-Wall -O2 -g -D_GNU_SOURCE
+CFLAGS+=	`[ "\`uname -s\`" = "Darwin" ] && echo "-DHAVE_STRLCPY -DHAVE_STRLCAT"`
 
 LDFLAGS+=	`pkg-config --libs fontconfig x11 xft xinerama xrandr`
 
diff --git a/calmwm.h b/calmwm.h
index c2e0b90..4a652e3 100644
--- a/calmwm.h
+++ b/calmwm.h
@@ -24,8 +24,12 @@
 /* prototypes for portable-included functions */
 char *fgetln(FILE *, size_t *);
 long long strtonum(const char *, long long, long long, const char **);
+#ifndef HAVE_STRLCPY
 size_t strlcpy(char *, const char *, size_t);
+#endif
+#ifndef HAVE_STRLCAT
 size_t strlcat(char *, const char *, size_t);
+#endif
 
 #include <X11/XKBlib.h>
 #include <X11/Xatom.h>