diff --git a/lib/web/test/helper.js b/lib/web/test/helper.js
index 6586f247..8a58dc97 100644
--- a/lib/web/test/helper.js
+++ b/lib/web/test/helper.js
@@ -1,8 +1,10 @@
 const release = '../../../target/release'
 const Parser = require(`${release}/tree-sitter.js`);
 const JavaScript = require.resolve(`${release}/tree-sitter-javascript.wasm`);
+const Python = require.resolve(`${release}/tree-sitter-python.wasm`);
 
 module.exports = Parser.init().then(async () => ({
   Parser,
   JavaScript: await Parser.Language.load(JavaScript),
+  Python: await Parser.Language.load(Python)
 }));
diff --git a/lib/web/test/parser-test.js b/lib/web/test/parser-test.js
index 991efc73..038ed59f 100644
--- a/lib/web/test/parser-test.js
+++ b/lib/web/test/parser-test.js
@@ -1,11 +1,11 @@
 const {assert} = require('chai');
-let Parser, JavaScript;
+let Parser, JavaScript, Python;
 
 describe("Parser", () => {
   let parser;
 
   before(async () =>
-    ({Parser, JavaScript} = await require('./helper'))
+    ({Parser, JavaScript, Python} = await require('./helper'))
   );
 
   beforeEach(() => {
@@ -125,6 +125,15 @@ describe("Parser", () => {
       assert.equal(tree.rootNode.firstChild.firstChild.namedChildCount, repeatCount);
     });
 
+    it.only("can use languages with external scanners written in C++", () => {
+      parser.setLanguage(Python);
+      tree = parser.parse("def foo():\n  bar()");
+      assert.equal(
+        tree.rootNode.toString(),
+        '(module (function_definition (identifier) (parameters) (expression_statement (call (identifier) (argument_list)))))'
+      );
+    });
+
     it('parses only the text within the `includedRanges` if they are specified', () => {
       const sourceCode = "<% foo() %> <% bar %>";
 
diff --git a/script/build-wasm b/script/build-wasm
index 819c601f..cc120f61 100755
--- a/script/build-wasm
+++ b/script/build-wasm
@@ -2,8 +2,6 @@
 
 set -e
 
-export EMCC_FORCE_STDLIBS=libc++
-
 args="-Os"
 if [[ "$1" == "--debug" ]]; then
   args="-s ASSERTIONS=1 SAFE_HEAP=1 -O0"
@@ -15,6 +13,7 @@ docker run                          \
   --rm                              \
   -v $(pwd):/src                    \
   -u $(id -u)                       \
+  -e EMCC_FORCE_STDLIBS=libc++      \
   trzeci/emscripten-slim            \
                                     \
   emcc                              \