http://lists.gnu.org/archive/html/openexr-devel/2013-04/msg00031.html

--- IlmImfCtl/ImfCtlApplyTransforms.h
+++ IlmImfCtl/ImfCtlApplyTransforms.h
@@ -186,12 +186,7 @@
 #include <vector>
 #include <ImathBox.h>
 #include <ImfThreading.h>
-
-namespace Imf
-{
-    class Header;
-    class FrameBuffer;
-}
+#include <ImfForward.h>
 
 namespace Ctl
 {