diff --git a/config.mk b/config.mk
index db0641c..e56d583 100644
--- a/config.mk
+++ b/config.mk
@@ -1,29 +1,37 @@
+OS := $(shell uname -s)
+
 # slock version
 VERSION = 1.5
 
-# Customize below to fit your system
-
 # paths
+ifeq ($(OS),FreeBSD)
 PREFIX = /usr/local
 MANPREFIX = ${PREFIX}/share/man
+else ifeq ($(OS),OpenBSD)
+PREFIX = /usr/local
+MANPREFIX = $(PREFIX)/man
+else
+PREFIX = /usr
+MANPREFIX = ${PREFIX}/share/man
+endif
 
 X11INC = /usr/X11R6/include
 X11LIB = /usr/X11R6/lib
 
 # includes and libs
-INCS = -I. -I/usr/include -I${X11INC}
-LIBS = -L/usr/lib -lc -lcrypt -L${X11LIB} -lX11 -lXext -lXrandr -lImlib2
+INCS = -I. -I${PREFIX}/include -I${X11INC}
+ifeq ($(OS),OpenBSD)
+LIBS = -L${PREFIX}/lib -lc -L${X11LIB} -lX11 -lXext -lXrandr -lImlib2
+else
+LIBS = -L${PREFIX}/lib -lc -lcrypt -L${X11LIB} -lX11 -lXext -lXrandr -lImlib2
+endif
 
 # flags
 CPPFLAGS = -DVERSION=\"${VERSION}\" -D_DEFAULT_SOURCE -DHAVE_SHADOW_H
 CFLAGS = -std=c99 -pedantic -Wall -Os ${INCS} ${CPPFLAGS}
 LDFLAGS = -s ${LIBS}
+ifeq ($(OS),OpenBSD)
+COMPATSRC =
+else
 COMPATSRC = explicit_bzero.c
-
-# On OpenBSD and Darwin remove -lcrypt from LIBS
-#LIBS = -L/usr/lib -lc -L${X11LIB} -lX11 -lXext -lXrandr
-# On *BSD remove -DHAVE_SHADOW_H from CPPFLAGS
-# On NetBSD add -D_NETBSD_SOURCE to CPPFLAGS
-#CPPFLAGS = -DVERSION=\"${VERSION}\" -D_BSD_SOURCE -D_NETBSD_SOURCE
-# On OpenBSD set COMPATSRC to empty
-#COMPATSRC =
+endif