diff --git a/zig-impl/makefile b/zig-impl/makefile
index e3e1181..6f8bba1 100644
--- a/zig-impl/makefile
+++ b/zig-impl/makefile
@@ -1,7 +1,9 @@
 all:
 
-ZIGC = zig
-ZIGOPTS = -OReleaseSmall $(ZIGUSROPTS)
+ZIGBUSEOPTS ?= -OReleaseSmall
+ZIGUSROPTS  ?= -freference-trace
+ZIGC        ?= zig
+ZIGOPTS     ?= $(ZIGBUSEOPTS) $(ZIGUSROPTS)
 
 c: src/send-msg.zig
 	$(ZIGC) build-exe $(ZIGOPTS) $^
@@ -16,7 +18,7 @@ t: src/main.zig
 	$(ZIGC) test $(ZIGOPTS) $^
 
 d: src/main.zig
-	$(ZIGC) build-exe $(ZIGOPTS) -freference-trace $^
+	$(ZIGC) build-exe $(ZIGOPTS) $^
 
 o: $(SRC)
 	$(ZIGC) test $(ZIGOPTS) $^