diff --git a/src/osgPlugins/glsl/ReaderWriterGLSL.cpp b/src/osgPlugins/glsl/ReaderWriterGLSL.cpp
index 61fcafbaa..45560b95e 100644
--- a/src/osgPlugins/glsl/ReaderWriterGLSL.cpp
+++ b/src/osgPlugins/glsl/ReaderWriterGLSL.cpp
@@ -62,7 +62,17 @@ class ReaderWriterGLSL : public osgDB::ReaderWriter
             osgDB::ifstream istream(fileName.c_str(), std::ios::in | std::ios::binary);
             if(!istream) return ReadResult::FILE_NOT_HANDLED;
             ReadResult rr = readShader(istream, options);
-            if(rr.validShader()) rr.getShader()->setFileName(file);
+            if(rr.validShader())
+            {
+                osg::Shader* shader = rr.getShader();
+                shader->setFileName(file);
+                if (shader->getType() == osg::Shader::UNDEFINED)
+                {
+                    // set type based on filename extension, where possible
+                    if (ext == "frag") shader->setType(osg::Shader::FRAGMENT);
+                    if (ext == "vert") shader->setType(osg::Shader::VERTEX);
+                }
+            }
             return rr;
         }