diff --git a/Makefile b/Makefile
index 630c945..c20e9df 100644
--- a/Makefile
+++ b/Makefile
@@ -40,10 +40,10 @@ target/$(CARGO_TARGET)/$(CARGO_PROFILE)/asteroids.wasm: $(SRCS) Cargo.lock Cargo
 out:
 	mkdir $@
 
-out/assets: out
+out/assets: | out
 	mkdir $@
 
-out/assets/%.ogg: out/assets assets/%.ogg
+out/assets/%.ogg: assets/%.ogg | out/assets
 	cp -ar assets/$*.ogg $@
 
 # Both the JS and WASM files are generated by the wasm-bindgen call, so both