diff --git a/src/osgPlugins/rgb/ReaderWriterRGB.cpp b/src/osgPlugins/rgb/ReaderWriterRGB.cpp
index ffaad7026..7cbd9a8cd 100644
--- a/src/osgPlugins/rgb/ReaderWriterRGB.cpp
+++ b/src/osgPlugins/rgb/ReaderWriterRGB.cpp
@@ -698,6 +698,9 @@ class ReaderWriterRGB : public osgDB::ReaderWriter
 
         virtual WriteResult writeImage(const osg::Image &img,const std::string& fileName, const osgDB::ReaderWriter::Options*) const
         {
+            std::string ext = osgDB::getFileExtension(fileName);
+            if (!acceptsExtension(ext)) return WriteResult::FILE_NOT_HANDLED;
+
             if (img.isCompressed())
             {
                 OSG_NOTICE<<"Warning: RGB plugin does not supporting writing compressed imagery."<<std::endl;
@@ -709,9 +712,6 @@ class ReaderWriterRGB : public osgDB::ReaderWriter
                 return WriteResult::ERROR_IN_WRITING_FILE;
             }
 
-            std::string ext = osgDB::getFileExtension(fileName);
-            if (!acceptsExtension(ext)) return WriteResult::FILE_NOT_HANDLED;
-
             osgDB::ofstream fout(fileName.c_str(), std::ios::out | std::ios::binary);
             if(!fout) return WriteResult::ERROR_IN_WRITING_FILE;