diff --git a/build/kvazaar_lib/kvazaar_lib.vcxproj b/build/kvazaar_lib/kvazaar_lib.vcxproj
index d3b59b61..9fc91d96 100644
--- a/build/kvazaar_lib/kvazaar_lib.vcxproj
+++ b/build/kvazaar_lib/kvazaar_lib.vcxproj
@@ -194,6 +194,7 @@
     <ClCompile Include="..\..\src\tables.c" />
     <ClCompile Include="..\..\src\threadqueue.c" />
     <ClCompile Include="..\..\src\transform.c" />
+    <ClInclude Include="..\..\src\kvazaar_internal.h" />
     <ClInclude Include="..\..\src\yuv_io.h" />
   </ItemGroup>
   <ItemGroup>
diff --git a/build/kvazaar_lib/kvazaar_lib.vcxproj.filters b/build/kvazaar_lib/kvazaar_lib.vcxproj.filters
index cbc3466f..4e221baa 100644
--- a/build/kvazaar_lib/kvazaar_lib.vcxproj.filters
+++ b/build/kvazaar_lib/kvazaar_lib.vcxproj.filters
@@ -353,6 +353,9 @@
     <ClInclude Include="..\..\src\yuv_io.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\src\kvazaar_internal.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <YASM Include="..\..\src\extras\x86inc.asm">
diff --git a/src/encmain.c b/src/encmain.c
index d522251f..2f9d7396 100644
--- a/src/encmain.c
+++ b/src/encmain.c
@@ -23,7 +23,7 @@
  *
  */
 
-#include "kvazaar.h"
+#include "kvazaar_internal.h"
 
 #ifdef _WIN32
 /* The following two defines must be located before the inclusion of any system header files. */
diff --git a/src/kvazaar.c b/src/kvazaar.c
index a4422225..e1f1fd05 100644
--- a/src/kvazaar.c
+++ b/src/kvazaar.c
@@ -18,7 +18,7 @@
 * with Kvazaar.  If not, see <http://www.gnu.org/licenses/>.
 ****************************************************************************/
 
-#include "kvazaar.h"
+#include "kvazaar_internal.h"
 
 #include <stdlib.h>
 
diff --git a/src/kvazaar.h b/src/kvazaar.h
index 92f86704..25488f19 100644
--- a/src/kvazaar.h
+++ b/src/kvazaar.h
@@ -51,6 +51,11 @@ typedef uint8_t kvz_pixel;
 typedef uint16_t kvz_pixel;
 #endif
 
+/**
+ * Opaque data structure representing one instance of the encoder.
+ */
+typedef struct kvz_encoder kvz_encoder;
+
 /**
  * \brief GoP picture configuration.
  */
@@ -137,9 +142,6 @@ typedef struct kvz_config
   int32_t target_bitrate;
 } kvz_config;
 
-typedef struct encoder_state_t encoder_state_t;
-typedef struct encoder_control_t encoder_control_t;
-
 /**
 * \brief Struct which contains all picture data
 */
@@ -176,20 +178,6 @@ typedef struct kvz_data_chunk {
   struct kvz_data_chunk *next;
 } kvz_data_chunk;
 
-/**
- * Main datastructure representing one instance of the encoder.
- */
-typedef struct kvz_encoder {
-  encoder_control_t* control;
-  encoder_state_t* states;
-  unsigned num_encoder_states;
-  unsigned cur_state_num;
-  unsigned frames_started;
-  unsigned frames_done;
-
-  size_t bitstream_length;
-} kvz_encoder;
-
 typedef struct kvz_api {
   kvz_config *  (*config_alloc)(void);
   int           (*config_destroy)(kvz_config *);
diff --git a/src/kvazaar_internal.h b/src/kvazaar_internal.h
new file mode 100644
index 00000000..5128daab
--- /dev/null
+++ b/src/kvazaar_internal.h
@@ -0,0 +1,40 @@
+#ifndef KVAZAAR_INTERNAL_H_
+#define KVAZAAR_INTERNAL_H_
+/*****************************************************************************
+* This file is part of Kvazaar HEVC encoder.
+*
+* Copyright (C) 2013-2015 Tampere University of Technology and others (see
+* COPYING file).
+*
+* Kvazaar is free software: you can redistribute it and/or modify it under
+* the terms of the GNU Lesser General Public License as published by the
+* Free Software Foundation; either version 2.1 of the License, or (at your
+* option) any later version.
+*
+* Kvazaar is distributed in the hope that it will be useful, but WITHOUT ANY
+* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+* FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
+* more details.
+*
+* You should have received a copy of the GNU General Public License along
+* with Kvazaar.  If not, see <http://www.gnu.org/licenses/>.
+****************************************************************************/
+
+#include "kvazaar.h"
+
+// Forward declarations.
+typedef struct encoder_state_t encoder_state_t;
+typedef struct encoder_control_t encoder_control_t;
+
+typedef struct kvz_encoder {
+  encoder_control_t* control;
+  encoder_state_t* states;
+  unsigned num_encoder_states;
+  unsigned cur_state_num;
+  unsigned frames_started;
+  unsigned frames_done;
+
+  size_t bitstream_length;
+} kvz_encoder;
+
+#endif // KVAZAAR_INTERNAL_H_