diff --git a/include/osgDB/ImageOptions b/include/osgDB/ImageOptions
index 6d2b05cd2..248f36401 100644
--- a/include/osgDB/ImageOptions
+++ b/include/osgDB/ImageOptions
@@ -26,7 +26,7 @@ class OSGDB_EXPORT ImageOptions : public osgDB::ReaderWriter::Options
         
         ImageOptions(const std::string& str);
             
-        ImageOptions(const ImageOptions& options,const osg::CopyOp copyop=osg::CopyOp::SHALLOW_COPY):
+        ImageOptions(const ImageOptions& options,const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY):
             osgDB::ReaderWriter::Options(options,copyop),
             _sourceImageSamplingMode(options._sourceImageSamplingMode),
             _sourceImageWindowMode(options._sourceImageWindowMode),