diff --git a/GenericIO.h b/GenericIO.h
index 2e893a35c76922c54ab9a87529580e15f230bb39..05a71f69926112b2d80fd54ae9acceed626fc1a2 100644
--- a/GenericIO.h
+++ b/GenericIO.h
@@ -347,7 +347,7 @@ public:
   }
 
 public:
-  std::size_t requestedExtraSpace() const {
+  static std::size_t requestedExtraSpace() {
     return 8;
   }