diff --git a/include/boost/python/str.hpp b/include/boost/python/str.hpp
index 72161c7b..758aa79e 100644
--- a/include/boost/python/str.hpp
+++ b/include/boost/python/str.hpp
@@ -5,6 +5,13 @@
 #include <boost/python/list.hpp>
 #include <boost/python/converter/pytype_object_manager_traits.hpp>
 
+// disable defines in <cctype> provided by some system libraries
+#undef isspace
+#undef islower
+#undef isalpha
+#undef isdigit
+#undef isalnum
+
 namespace boost { namespace python {
 
 class str : public object