diff --git a/Makefile b/Makefile
index ca7f0bf..771cdf5 100644
--- a/Makefile
+++ b/Makefile
@@ -61,7 +61,7 @@ ifneq ($(HAS_SERVER),)
 endif
 
 ## Ensures NPM dependencies are installed without having to run this all the time.
-webapp/.npminstall:
+webapp/.npminstall: webapp/package.json
 ifneq ($(HAS_WEBAPP),)
 	cd webapp && $(NPM) install
 	touch $@