diff --git a/Makefile b/Makefile
index 3f1921d75..9fe8d1ff9 100644
--- a/Makefile
+++ b/Makefile
@@ -33,13 +33,10 @@ SITEPACKAGES=root/lib/python$(PYMINOR)/site-packages
 all: build/pyodide.asm.html build/pyodide.js
 
 
-build:
-	[ -d build ] || mkdir build
-
-
 build/pyodide.asm.html: src/main.bc src/jsimport.bc src/jsproxy.bc src/js2python.bc \
                         src/pyimport.bc src/pyproxy.bc src/python2js.bc \
-												src/runpython.bc root/.built build
+												src/runpython.bc root/.built
+	[ -d build ] || mkdir build
 	$(CC) -s EXPORT_NAME="'pyodide'" --bind -o $@ $(filter %.bc,$^) $(LDFLAGS) \
 		$(foreach d,$(wildcard root/*),--preload-file $d@/$(notdir $d))
 
@@ -52,7 +49,7 @@ clean:
 	rm -fr root
 	rm build/*
 	rm src/*.bc
-	echo "CPython and Numpy builds were not cleaned"
+	echo "CPython and Numpy builds are not cleaned. cd into those directories to do so."
 
 
 %.bc: %.cpp $(CPYTHONLIB)
@@ -65,7 +62,7 @@ root/.built: \
 		src/lazy_import.py \
 		src/sitecustomize.py \
 		remove_modules.txt
-	[ -d root ] && rm -rf root
+	rm -rf root
 	mkdir -p root/lib
 	cp -a $(CPYTHONLIB)/ root/lib
 	cp -a numpy/build/numpy $(SITEPACKAGES)
diff --git a/numpy/Makefile b/numpy/Makefile
index 7df5fc11b..e00af3b5c 100644
--- a/numpy/Makefile
+++ b/numpy/Makefile
@@ -45,6 +45,7 @@ LDFLAGS=-Werror \
 
 
 all: \
+	$(BUILD)/numpy/__init__.py \
 	$(BUILDCORE)/multiarray.so \
 	$(BUILDCORE)/umath.so \
 	$(BUILDLINALG)/lapack_lite.so \
@@ -70,18 +71,18 @@ $(HOSTDIR)/setup.py: $(ZIPFILE)
 	touch $(HOSTDIR)/setup.py
 
 
-$(GENSRC)/multiarray/arraytypes.c: $(ROOT)/.patched
+$(HOSTBUILD)/lib.$(PLATFORMSLUG)/numpy/__init__.py: $(ROOT)/.patched
 	( \
 	  cd $(HOSTDIR); \
     $(HOSTPYTHON) setup.py build \
 	)
 
 
-$(BUILD)/numpy/__init__.py: $(GENSRC)/multiarray/arraytypes.c
+$(BUILD)/numpy/__init__.py: $(HOSTBUILD)/lib.$(PLATFORMSLUG)/numpy/__init__.py
 	[ -d $(BUILD) ] || mkdir $(BUILD)
 	cp -r $(HOSTBUILD)/lib.$(PLATFORMSLUG)/numpy $(BUILD) && \
 	cd $(BUILD); find . -name "*.so" -type f -delete
-
+	touch $(BUILD)/numpy/__init__.py
 
 $(ROOT)/.patched: $(HOSTDIR)/setup.py
 	cat patches/*.patch | (cd $(HOSTDIR) ; patch -p1)