diff --git a/libsrc/core/python_ngcore.hpp b/libsrc/core/python_ngcore.hpp
index 49136e53..b3e428b3 100644
--- a/libsrc/core/python_ngcore.hpp
+++ b/libsrc/core/python_ngcore.hpp
@@ -50,7 +50,9 @@ namespace ngcore
   {
       using TFlat = FlatArray<T, TIND>;
       using TArray = Array<T, TIND>;
-      std::string suffix = std::string(typeid(T).name()) + "_" + typeid(TIND).name();
+      std::string suffix = std::string(Demangle(typeid(T).name())) + "_" + Demangle(typeid(TIND).name());
+      std::replace(suffix.begin(), suffix.end(), ':', '_');
+      std::replace(suffix.begin(), suffix.end(), ' ', '_');
       std::string fname = std::string("FlatArray_") + suffix;
       auto flatarray_class = py::class_<TFlat>(m, fname.c_str(),
                                                py::buffer_protocol())
diff --git a/tests/pytest/test_array.py b/tests/pytest/test_array.py
index ccd186c1..54c48755 100644
--- a/tests/pytest/test_array.py
+++ b/tests/pytest/test_array.py
@@ -2,7 +2,7 @@ from pyngcore import *
 from numpy import sort, array
 
 def test_array_numpy():
-    a = Array_i_m(5)
+    a = Array_int_unsigned_long(5)
     a[:] = 0
     a[3:] = 2
     assert(sum(a) == 4)