@@ -166,8 +166,11 @@
         if (!ready) { Module.print('Python is loading, please wait...'); return; }
         Module.print('>>> <textarea>');
         source_code = document.getElementById('file').value;
-        Module.cwrap('PyRun_SimpleString', 'number', ['string'])(source_code);
-        // or: Module.ccall('PyRun_SimpleString', 'number', ['string'], [source_code]);
+        var opts = {}
+        if (typeof Asyncify === 'object')
+            opts = { async: true };
+        Module.cwrap('PyRun_SimpleString', 'number', ['string'], opts)(source_code);
+        // or: Module.ccall('PyRun_SimpleString', 'number', ['string'], [source_code], opts);
       }
 
       var hist = [''];
@@ -179,8 +182,11 @@
           Module.print('>>> ' + input.value);
 
           // Execute Python code with emulated stdin
-          FS.writeFile('/tmp/input.py', input.value + '\n')
-          Module.ccall('pyruni');
+          FS.writeFile('/tmp/input.py', input.value + '\n');
+          var opts = {}
+          if (typeof Asyncify === 'object')
+              opts = { async: true };
+          Module.ccall('pyruni', 'undefined', [], [], opts);
 
           hist[hist.length-1] = input.value;
           hist.push('');
 
@@ -23,9 +23,13 @@ PREFIX=$INSTALLDIR OUTDIR=$BUILD ./package-pythonhome.sh \
     encodings/utf_32_be.py
 
 FLAGS='-O3'
-if [ "$1" == "debug" ]; then
-    FLAGS='-s ASSERTIONS=1 -g -s FETCH_DEBUG=1'
-fi
+while (( $# )); do
+    case "$1" in
+	debug) FLAGS='-s ASSERTIONS=1 -g -s FETCH_DEBUG=1';;
+	async) ASYNC='-s ASYNCIFY=1 -O3';;
+    esac
+    shift
+done
 emcc -o $BUILD/index.html \
   webprompt-main.c $BUILD/emscripten.c \
   $FLAGS \
@@ -35,10 +39,10 @@ emcc -o $BUILD/index.html \
   -s FETCH=1 \
   -s ALLOW_MEMORY_GROWTH=1 \
   -s FORCE_FILESYSTEM=1 -s RETAIN_COMPILER_SETTINGS=1 \
+  $ASYNC \
   --shell-file webprompt-shell.html -s MINIFY_HTML=0 \
-  -s EXPORTED_FUNCTIONS="['_main', '_Py_Initialize', '_PyRun_SimpleString', '_pyruni']" \
-  -s EXTRA_EXPORTED_RUNTIME_METHODS='["ccall", "cwrap"]'
-# -s ASYNCIFY=1
+  -s EXPORTED_FUNCTIONS='[_main, _Py_Initialize, _PyRun_SimpleString, _pyruni, _emscripten_debugger]' \
+  -s EXTRA_EXPORTED_RUNTIME_METHODS='[ccall, cwrap]'
 
 # cython ../mock/emscripten.pyx -o t/mock.c
 # gcc -g -I build/hostpython/include/python2.7 -L build/hostpython/lib/ t/mock.c webprompt-main.c -lpython2.7 -ldl -lm -lutil -lz