diff --git a/darkwater/DW640.h b/darkwater/DW640.h
index 8c5a61b..c9fcfa1 100644
--- a/darkwater/DW640.h
+++ b/darkwater/DW640.h
@@ -59,6 +59,8 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 using namespace DarkWater;
 
+class DW640;
+
 class DW_Motor {
     public:
         DW_Motor(void);