diff --git a/include/osg/FrameBufferObject b/include/osg/FrameBufferObject
index 4401450b1..bd31859ea 100644
--- a/include/osg/FrameBufferObject
+++ b/include/osg/FrameBufferObject
@@ -360,12 +360,12 @@ namespace osg
         FrameBufferAttachment(const FrameBufferAttachment& copy);
 
         explicit FrameBufferAttachment(RenderBuffer* target);
-        explicit FrameBufferAttachment(Texture1D* target, int level = 0);
-        explicit FrameBufferAttachment(Texture2D* target, int level = 0);
-        explicit FrameBufferAttachment(Texture2DMultisample* target, int level = 0);
-        explicit FrameBufferAttachment(Texture3D* target, int zoffset, int level = 0);
-        explicit FrameBufferAttachment(Texture2DArray* target, int layer, int level = 0);
-        explicit FrameBufferAttachment(TextureCubeMap* target, int face, int level = 0);
+        explicit FrameBufferAttachment(Texture1D* target, unsigned int level = 0);
+        explicit FrameBufferAttachment(Texture2D* target, unsigned int level = 0);
+        explicit FrameBufferAttachment(Texture2DMultisample* target, unsigned int level = 0);
+        explicit FrameBufferAttachment(Texture3D* target, unsigned int zoffset, unsigned int level = 0);
+        explicit FrameBufferAttachment(Texture2DArray* target, unsigned int layer, unsigned int level = 0);
+        explicit FrameBufferAttachment(TextureCubeMap* target, unsigned int face, unsigned int level = 0);
         explicit FrameBufferAttachment(TextureRectangle* target);
         explicit FrameBufferAttachment(Camera::Attachment& attachment);
         
@@ -384,10 +384,10 @@ namespace osg
         Texture* getTexture();
         const Texture* getTexture() const;
 
-        int getCubeMapFace() const;
-        int getTextureLevel() const;
-        int getTexture3DZOffset() const;
-        int getTextureArrayLayer() const;
+        unsigned int getCubeMapFace() const;
+        unsigned int getTextureLevel() const;
+        unsigned int getTexture3DZOffset() const;
+        unsigned int getTextureArrayLayer() const;
 
     private:
         // use the Pimpl idiom to avoid dependency from
diff --git a/src/osg/FrameBufferObject.cpp b/src/osg/FrameBufferObject.cpp
index ce94c3014..65ff37780 100644
--- a/src/osg/FrameBufferObject.cpp
+++ b/src/osg/FrameBufferObject.cpp
@@ -89,14 +89,18 @@ FBOExtensions::FBOExtensions(unsigned int contextID)
         glDeleteFramebuffers != 0 &&
         glGenFramebuffers != 0 &&
         glCheckFramebufferStatus != 0 &&
-        glFramebufferTexture1D != 0 &&
         glFramebufferTexture2D != 0 &&
-        glFramebufferTexture3D != 0 &&
-        glFramebufferTexture != 0 &&
         glFramebufferRenderbuffer != 0 &&
         glGenerateMipmap != 0 &&
         glGetRenderbufferParameteriv != 0;
 
+#if !defined(OSG_GLES1_AVAILABLE) && !defined(OSG_GLES2_AVAILABLE)
+    _supported = _supported &&
+        glFramebufferTexture1D != 0 &&
+        glFramebufferTexture3D != 0 &&
+        glFramebufferTexture != 0;
+#endif
+
     LOAD_FBO_EXT(glBlitFramebuffer);
     LOAD_FBO_EXT(glRenderbufferStorageMultisample);
     LOAD_FBO_EXT(glRenderbufferStorageMultisampleCoverageNV);
@@ -298,11 +302,11 @@ struct FrameBufferAttachment::Pimpl
     TargetType targetType;
     ref_ptr<RenderBuffer> renderbufferTarget;
     ref_ptr<Texture> textureTarget;
-    int cubeMapFace;
-    int level;
-    int zoffset;
+    unsigned int cubeMapFace;
+    unsigned int level;
+    unsigned int zoffset;
 
-    explicit Pimpl(TargetType ttype = RENDERBUFFER, int lev = 0)
+    explicit Pimpl(TargetType ttype = RENDERBUFFER, unsigned int lev = 0)
     :    targetType(ttype),
         cubeMapFace(0),
         level(lev),
@@ -337,39 +341,39 @@ FrameBufferAttachment::FrameBufferAttachment(RenderBuffer* target)
     _ximpl->renderbufferTarget = target;
 }
 
-FrameBufferAttachment::FrameBufferAttachment(Texture1D* target, int level)
+FrameBufferAttachment::FrameBufferAttachment(Texture1D* target, unsigned int level)
 {
     _ximpl = new Pimpl(Pimpl::TEXTURE1D, level);
     _ximpl->textureTarget = target;
 }
 
-FrameBufferAttachment::FrameBufferAttachment(Texture2D* target, int level)
+FrameBufferAttachment::FrameBufferAttachment(Texture2D* target, unsigned int level)
 {
     _ximpl = new Pimpl(Pimpl::TEXTURE2D, level);
     _ximpl->textureTarget = target;
 }
 
-FrameBufferAttachment::FrameBufferAttachment(Texture2DMultisample* target, int level)
+FrameBufferAttachment::FrameBufferAttachment(Texture2DMultisample* target, unsigned int level)
 {
     _ximpl = new Pimpl(Pimpl::TEXTURE2DMULTISAMPLE, level);
     _ximpl->textureTarget = target;
 }
 
-FrameBufferAttachment::FrameBufferAttachment(Texture3D* target, int zoffset, int level)
+FrameBufferAttachment::FrameBufferAttachment(Texture3D* target, unsigned int zoffset, unsigned int level)
 {
     _ximpl = new Pimpl(Pimpl::TEXTURE3D, level);
     _ximpl->textureTarget = target;
     _ximpl->zoffset = zoffset;
 }
 
-FrameBufferAttachment::FrameBufferAttachment(Texture2DArray* target, int layer, int level)
+FrameBufferAttachment::FrameBufferAttachment(Texture2DArray* target, unsigned int layer, unsigned int level)
 {
     _ximpl = new Pimpl(Pimpl::TEXTURE2DARRAY, level);
     _ximpl->textureTarget = target;
     _ximpl->zoffset = layer;
 }
 
-FrameBufferAttachment::FrameBufferAttachment(TextureCubeMap* target, int face, int level)
+FrameBufferAttachment::FrameBufferAttachment(TextureCubeMap* target, unsigned int face, unsigned int level)
 {
     _ximpl = new Pimpl(Pimpl::TEXTURECUBE, level);
     _ximpl->textureTarget = target;
@@ -618,22 +622,22 @@ const Texture* FrameBufferAttachment::getTexture() const
     return _ximpl->textureTarget.get();
 }
 
-int FrameBufferAttachment::getCubeMapFace() const
+unsigned int FrameBufferAttachment::getCubeMapFace() const
 {
     return _ximpl->cubeMapFace;
 }
 
-int FrameBufferAttachment::getTextureLevel() const
+unsigned int FrameBufferAttachment::getTextureLevel() const
 {
     return _ximpl->level;
 }
 
-int FrameBufferAttachment::getTexture3DZOffset() const
+unsigned int FrameBufferAttachment::getTexture3DZOffset() const
 {
     return _ximpl->zoffset;
 }
 
-int FrameBufferAttachment::getTextureArrayLayer() const
+unsigned int FrameBufferAttachment::getTextureArrayLayer() const
 {
     return _ximpl->zoffset;
 }