diff --git a/src/python2js.c b/src/python2js.c
index 633f99c8a..e003e34c0 100644
--- a/src/python2js.c
+++ b/src/python2js.c
@@ -134,7 +134,7 @@ _python2js(PyObject* x, PyObject* map)
     // Since Javascript doesn't support > 32-bit ints, use floats
     // when the Python int gets too large.  This will lose precision,
     // but is less problematic than truncation.
-    if ((unsigned long)x_long > 0x7fffffff) {
+    if (labs(x_long) > 0x7fffffff) {
       PyObject* py_float = PyNumber_Float(x);
       if (py_float == NULL) {
         return HW_ERROR;
diff --git a/test/test_python.py b/test/test_python.py
index 279384ab8..83ef16f2c 100644
--- a/test/test_python.py
+++ b/test/test_python.py
@@ -63,6 +63,8 @@ def test_python2js_long_ints(selenium):
     assert selenium.run('2**31') == 2**31
     assert selenium.run('2**30 - 1 + 2**30') == (2**30 - 1 + 2**30)
     assert selenium.run('2**32 / 2**4') == (2**32 / 2**4)
+    assert selenium.run('-2**30') == -2**30
+    assert selenium.run('-2**31') == -2**31
 
 
 def test_pythonexc2js(selenium):