--- a/SignalFreeBackgroundEstimator/Makefile
+++ b/SignalFreeBackgroundEstimator/Makefile
@@ -39,8 +39,8 @@
 all: lib$(NAME).a
 
 lib$(NAME).a: $(OBJS) 
-	ar cru lib$(NAME).a $(OBJS)
-	ranlib lib$(NAME).a
+	$(AR) cru lib$(NAME).a $(OBJS)
+	$(RANLIB) lib$(NAME).a
 
 # building the examples
 examples: $(EXAMPLES)