diff --git a/example/example20.cpp b/example/example20.cpp
index 2535b25..7066e32 100644
--- a/example/example20.cpp
+++ b/example/example20.cpp
@@ -57,7 +57,13 @@
         ptr[i].b.x = (i + 1) % 2; ptr[i].b.y = (uint32_t) (i + 1); ptr[i].b.z = (float) (i + 1) * 1.5f;
     }
     return arr;
+}
 
+
+void print_format_descriptors() {
+    std::cout << py::format_descriptor<Struct>::value() << std::endl;
+    std::cout << py::format_descriptor<PackedStruct>::value() << std::endl;
+    std::cout << py::format_descriptor<NestedStruct>::value() << std::endl;
 }
 
 void init_ex20(py::module &m) {
@@ -68,4 +74,5 @@
     m.def("create_rec_simple", &create_recarray<Struct>);
     m.def("create_rec_packed", &create_recarray<PackedStruct>);
     m.def("create_rec_nested", &create_nested);
+    m.def("print_format_descriptors", &print_format_descriptors);
 }
diff --git a/example/example20.py b/example/example20.py
index 83725b5..83a914c 100644
--- a/example/example20.py
+++ b/example/example20.py
@@ -2,12 +2,16 @@
 from __future__ import print_function
 
 import numpy as np
-from example import create_rec_simple, create_rec_packed, create_rec_nested
+from example import (
+    create_rec_simple, create_rec_packed, create_rec_nested, print_format_descriptors
+)
 
 
 def check_eq(arr, data, dtype):
     np.testing.assert_equal(arr, np.array(data, dtype=dtype))
 
+print_format_descriptors()
+
 simple_dtype = np.dtype({'names': ['x', 'y', 'z'],
                          'formats': ['?', 'u4', 'f4'],
                          'offsets': [0, 4, 8]})
diff --git a/example/example20.ref b/example/example20.ref
index e69de29..6023a87 100644
--- a/example/example20.ref
+++ b/example/example20.ref
@@ -0,0 +1,3 @@
+T{?:x:xxxI:y:f:z:}
+T{?:x:=I:y:f:z:}
+T{T{?:x:xxxI:y:f:z:}:a:T{?:x:=I:y:f:z:}:b:}