diff --git a/src/runtime/c/gu/exn.h b/src/runtime/c/gu/exn.h
index 66ca107e3..36e52917f 100644
--- a/src/runtime/c/gu/exn.h
+++ b/src/runtime/c/gu/exn.h
@@ -91,8 +91,11 @@ gu_exn_clear(GuExn* err) {
 GuType*
 gu_exn_caught(GuExn* err);
 
-const void*
-gu_exn_caught_data(GuExn* err);
+inline const void*
+gu_exn_caught_data(GuExn* err)
+{
+	return err->data.data;
+}
 
 /// Temporarily block a raised exception.
 void
diff --git a/src/runtime/python/pypgf.c b/src/runtime/python/pypgf.c
index fa5103615..7fd6c5cdf 100644
--- a/src/runtime/python/pypgf.c
+++ b/src/runtime/python/pypgf.c
@@ -1640,7 +1640,12 @@ pgf_readPGF(PyObject *self, PyObject *args)
 	// Read the PGF grammar.
 	py_pgf->pgf = pgf_read(fpath, py_pgf->pool, err);
 	if (!gu_ok(err)) {
-		PyErr_SetString(PGFError, "The grammar cannot be loaded");
+		if (gu_exn_caught(err) == gu_type(GuErrno)) {
+			errno = *((GuErrno*) gu_exn_caught_data(err));
+			PyErr_SetFromErrnoWithFilename(PyExc_IOError, fpath);
+		} else {
+			PyErr_SetString(PGFError, "The grammar cannot be loaded");
+		}
 		Py_DECREF(py_pgf);
 		gu_pool_free(tmp_pool);
 		return NULL;