Cast the result of xxxPyCObject_Import to PycStringIO_CAPI*.
This fixes bug #431557.
diff --git a/Include/cStringIO.h b/Include/cStringIO.h
index 8aff2e3..cb8f337 100644
--- a/Include/cStringIO.h
+++ b/Include/cStringIO.h
@@ -126,6 +126,6 @@
 }
 
 #define PycString_IMPORT \
-  PycStringIO=xxxPyCObject_Import("cStringIO", "cStringIO_CAPI")
+  PycStringIO=(struct PycStringIO_CAPI*)xxxPyCObject_Import("cStringIO", "cStringIO_CAPI")
 
 #endif /* CSTRINGIO_INCLUDED */