diff --git a/CMakeLists.txt b/CMakeLists.txt
index b4030d1..9ff6e9b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,13 +10,10 @@ message(WARNING "Version to build: ${GRIVE_VERSION}")
 # common compile options
 add_definitions( -DVERSION="${GRIVE_VERSION}" )
 add_definitions( -D_FILE_OFFSET_BITS=64 -std=c++0x )
-if ( APPLE )
-	add_definitions( -Doff64_t=off_t )
-endif ( APPLE )
 
-if ( CMAKE_SYSTEM MATCHES "^FreeBSD" )
+if ( APPLE OR ${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD" OR ${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD" )
 	add_definitions( -Doff64_t=off_t )
-endif ( CMAKE_SYSTEM MATCHES "^FreeBSD" )
+endif ( APPLE OR ${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD" OR ${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD" )
 
 find_program(
 	HAVE_SYSTEMD systemd