diff --git a/CommandLineArguments.hxx.in b/CommandLineArguments.hxx.in
index 68f2f5d0694cee80035c1073e46b8458ca340e23..01b292f6588bf0917050433b4fe7537450d3a036 100644
--- a/CommandLineArguments.hxx.in
+++ b/CommandLineArguments.hxx.in
@@ -29,7 +29,7 @@ namespace @KWSYS_NAMESPACE@
 {
 
 class CommandLineArgumentsInternal;
-class CommandLineArgumentsCallbackStructure;
+struct CommandLineArgumentsCallbackStructure;
 
 /** \class CommandLineArguments
  * \brief Command line arguments processing code.