diff --git a/io/catchiofailure.cpp b/io/catchiofailure.cpp
index cd0435f..2dd382d 100644
--- a/io/catchiofailure.cpp
+++ b/io/catchiofailure.cpp
@@ -1,12 +1,13 @@
+// include libstd++ specific header <bits/c++config.h> containing _GLIBCXX_RELEASE
+// without including ios already (must be included after setting _GLIBCXX_USE_CXX11_ABI)
+#include <cctype>
+
 // ensure the old ABI is used under libstd++ < 7 and the new ABI under libstd++ >= 7
-#ifdef _GLIBCXX_RELEASE
-#include <bits/c++config.h>
-#if _GLIBCXX_RELEASE >= 7
+#if defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE >= 7
 #define _GLIBCXX_USE_CXX11_ABI 1
 #else
 #define _GLIBCXX_USE_CXX11_ABI 0
 #endif
-#endif
 
 #include "./catchiofailure.h"