diff --git a/include/openPMD/IO/IOTask.hpp b/include/openPMD/IO/IOTask.hpp
index f8d08ab821..d4db58483b 100644
--- a/include/openPMD/IO/IOTask.hpp
+++ b/include/openPMD/IO/IOTask.hpp
@@ -67,7 +67,7 @@ namespace internal
      * The returned strings are compile-time constants, so no worries about
      * pointer validity.
      */
-    std::string operationAsString(Operation);
+    OPENPMDAPI_EXPORT std::string operationAsString(Operation);
 } // namespace internal
 
 struct OPENPMDAPI_EXPORT AbstractParameter