diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index a22a63dd..e7017d71 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -39,6 +39,7 @@ SET( LIBEXIV2_PRIVATE_HDR cr2image_int.hpp
                           pngchunk_int.hpp
                           rcsid_int.hpp
                           rw2image_int.hpp
+                          sigmamn_int.hpp
                           tiffcomposite_int.hpp
                           tifffwd_int.hpp
                           tiffimage_int.hpp
@@ -76,7 +77,6 @@ SET( LIBEXIV2_HDR         basicio.hpp
                           psdimage.hpp
                           rafimage.hpp
                           rw2image.hpp
-                          sigmamn.hpp
                           sonymn.hpp
                           tags.hpp
                           tgaimage.hpp
diff --git a/src/sigmamn.cpp b/src/sigmamn.cpp
index 4d2eb336..dfdce665 100644
--- a/src/sigmamn.cpp
+++ b/src/sigmamn.cpp
@@ -34,7 +34,7 @@ EXIV2_RCSID("@(#) $Id$")
 // *****************************************************************************
 // included header files
 #include "types.hpp"
-#include "sigmamn.hpp"
+#include "sigmamn_int.hpp"
 #include "value.hpp"
 #include "i18n.h"                // NLS support.
 
@@ -48,6 +48,7 @@ EXIV2_RCSID("@(#) $Id$")
 // *****************************************************************************
 // class member definitions
 namespace Exiv2 {
+    namespace Internal {
 
     // Sigma (Foveon) MakerNote Tag Info
     const TagInfo SigmaMakerNote::tagInfo_[] = {
@@ -170,4 +171,4 @@ namespace Exiv2 {
         return os;
     }
 
-}                                       // namespace Exiv2
+}}                                      // namespace Internal, Exiv2
diff --git a/src/sigmamn.hpp b/src/sigmamn_int.hpp
similarity index 90%
rename from src/sigmamn.hpp
rename to src/sigmamn_int.hpp
index d2a9e093..0964470a 100644
--- a/src/sigmamn.hpp
+++ b/src/sigmamn_int.hpp
@@ -19,7 +19,7 @@
  * Foundation, Inc., 51 Franklin Street, 5th Floor, Boston, MA 02110-1301 USA.
  */
 /*!
-  @file    sigmamn.hpp
+  @file    sigmamn_int.hpp
   @brief   Sigma and Foveon MakerNote implemented according to the specification
            <a href="http://www.x3f.info/technotes/FileDocs/MakerNoteDoc.html">
            SIGMA and FOVEON EXIF MakerNote Documentation</a> by Foveon.
@@ -28,8 +28,8 @@
            <a href="mailto:ahuggel@gmx.net">ahuggel@gmx.net</a>
   @date    02-Apr-04, ahu: created
  */
-#ifndef SIGMAMN_HPP_
-#define SIGMAMN_HPP_
+#ifndef SIGMAMN_INT_HPP_
+#define SIGMAMN_INT_HPP_
 
 // *****************************************************************************
 // included header files
@@ -44,12 +44,13 @@
 // *****************************************************************************
 // namespace extensions
 namespace Exiv2 {
+    namespace Internal {
 
 // *****************************************************************************
 // class definitions
 
     //! MakerNote for Sigma (Foveon) cameras
-    class EXIV2API SigmaMakerNote {
+    class SigmaMakerNote {
     public:
         //! Return read-only list of built-in Sigma tags
         static const TagInfo* tagList();
@@ -70,6 +71,6 @@ namespace Exiv2 {
 
     }; // class SigmaMakerNote
 
-}                                       // namespace Exiv2
+}}                                      // namespace Internal, Exiv2
 
-#endif                                  // #ifndef SIGMAMN_HPP_
+#endif                                  // #ifndef SIGMAMN_INT_HPP_
diff --git a/src/tags.cpp b/src/tags.cpp
index aa4993a9..82292989 100644
--- a/src/tags.cpp
+++ b/src/tags.cpp
@@ -44,7 +44,7 @@ EXIV2_RCSID("@(#) $Id$")
 #include "olympusmn.hpp"
 #include "panasonicmn_int.hpp"
 #include "pentaxmn_int.hpp"
-#include "sigmamn.hpp"
+#include "sigmamn_int.hpp"
 #include "sonymn.hpp"
 #include "i18n.h"                // NLS support.