diff --git a/README.md b/README.md
index 90ce5119..b2601da3 100644
--- a/README.md
+++ b/README.md
@@ -69,7 +69,7 @@ You may want to test out changes in the emulator first. To do this, you'll need
 ```
 cd movement/make
 emmake make
-python3 -m http.server 8000 -d build
+python3 -m http.server -d build-sim
 ```
 
 Finally, visit [watch.html](http://localhost:8000/watch.html) to see your work.
diff --git a/make.mk b/make.mk
index 2fe89d75..446ad6fe 100644
--- a/make.mk
+++ b/make.mk
@@ -1,5 +1,9 @@
 ##############################################################################
+ifndef EMSCRIPTEN
 BUILD = ./build
+else
+BUILD = ./build-sim
+endif
 BIN = watch
 
 ifndef BOARD
diff --git a/movement/make/make_alternate_fw.sh b/movement/make/make_alternate_fw.sh
index 575c9e52..739c8557 100755
--- a/movement/make/make_alternate_fw.sh
+++ b/movement/make/make_alternate_fw.sh
@@ -28,9 +28,9 @@ do
     make clean
     emmake make FIRMWARE=$VARIANT
     mkdir "$sim_dir/$variant/"
-    mv "build/watch.wasm" "$sim_dir/$variant/"
-    mv "build/watch.js" "$sim_dir/$variant/"
-    mv "build/watch.html" "$sim_dir/$variant/index.html"
+    mv "build-sim/watch.wasm" "$sim_dir/$variant/"
+    mv "build-sim/watch.js" "$sim_dir/$variant/"
+    mv "build-sim/watch.html" "$sim_dir/$variant/index.html"
 done
 
 echo "Done."