diff --git a/src/sound/i_sound.cpp b/src/sound/i_sound.cpp
index 88cece9d4..ec2071106 100644
--- a/src/sound/i_sound.cpp
+++ b/src/sound/i_sound.cpp
@@ -56,6 +56,9 @@ extern HINSTANCE g_hInst;
 #include "fmodsound.h"
 #include "oalsound.h"
 
+#include "mpg123_decoder.h"
+#include "sndfile_decoder.h"
+
 #include "m_swap.h"
 #include "stats.h"
 #include "files.h"
diff --git a/src/sound/i_soundinternal.h b/src/sound/i_soundinternal.h
index dd9fb35f8..14dadf3e2 100644
--- a/src/sound/i_soundinternal.h
+++ b/src/sound/i_soundinternal.h
@@ -139,88 +139,4 @@ private:
     SoundDecoder& operator=(const SoundDecoder &rhs);
 };
 
-#ifdef HAVE_MPG123
-#include "mpg123.h"
-struct MPG123Decoder : public SoundDecoder
-{
-    virtual void getInfo(int *samplerate, ChannelConfig *chans, SampleType *type);
-
-    virtual size_t read(char *buffer, size_t bytes);
-    virtual bool seek(size_t ms_offset);
-    virtual size_t getSampleOffset();
-
-    MPG123Decoder() : MPG123(0), File(0) { }
-    virtual ~MPG123Decoder();
-
-protected:
-    virtual bool open(const char *data, size_t length);
-    virtual bool open(const char *fname, size_t offset, size_t length);
-
-private:
-    mpg123_handle *MPG123;
-    bool Done;
-
-    FILE *File;
-    size_t FileLength;
-    size_t FileOffset;
-    static off_t file_lseek(void *handle, off_t offset, int whence);
-    static ssize_t file_read(void *handle, void *buffer, size_t bytes);
-
-    const char *MemData;
-    size_t MemLength;
-    size_t MemPos;
-    static off_t mem_lseek(void *handle, off_t offset, int whence);
-    static ssize_t mem_read(void *handle, void *buffer, size_t bytes);
-
-    // Make non-copyable
-    MPG123Decoder(const MPG123Decoder &rhs);
-    MPG123Decoder& operator=(const MPG123Decoder &rhs);
-};
-#endif
-#ifdef HAVE_SNDFILE
-#include "sndfile.h"
-struct SndFileDecoder : public SoundDecoder
-{
-    virtual void getInfo(int *samplerate, ChannelConfig *chans, SampleType *type);
-
-    virtual size_t read(char *buffer, size_t bytes);
-    virtual std::vector<char> readAll();
-    virtual bool seek(size_t ms_offset);
-    virtual size_t getSampleOffset();
-
-    SndFileDecoder() : SndFile(0), File(0) { }
-    virtual ~SndFileDecoder();
-
-protected:
-    virtual bool open(const char *data, size_t length);
-    virtual bool open(const char *fname, size_t offset, size_t length);
-
-private:
-    SNDFILE *SndFile;
-    SF_INFO SndInfo;
-
-    FILE *File;
-    size_t FileLength;
-    size_t FileOffset;
-    static sf_count_t file_get_filelen(void *user_data);
-    static sf_count_t file_seek(sf_count_t offset, int whence, void *user_data);
-    static sf_count_t file_read(void *ptr, sf_count_t count, void *user_data);
-    static sf_count_t file_write(const void *ptr, sf_count_t count, void *user_data);
-    static sf_count_t file_tell(void *user_data);
-
-    const char *MemData;
-    size_t MemLength;
-    size_t MemPos;
-    static sf_count_t mem_get_filelen(void *user_data);
-    static sf_count_t mem_seek(sf_count_t offset, int whence, void *user_data);
-    static sf_count_t mem_read(void *ptr, sf_count_t count, void *user_data);
-    static sf_count_t mem_write(const void *ptr, sf_count_t count, void *user_data);
-    static sf_count_t mem_tell(void *user_data);
-
-    // Make non-copyable
-    SndFileDecoder(const SndFileDecoder &rhs);
-    SndFileDecoder& operator=(const SndFileDecoder &rhs);
-};
-#endif
-
 #endif
diff --git a/src/sound/mpg123_decoder.cpp b/src/sound/mpg123_decoder.cpp
index bacb7df46..c3a811b40 100644
--- a/src/sound/mpg123_decoder.cpp
+++ b/src/sound/mpg123_decoder.cpp
@@ -1,4 +1,4 @@
-#include "i_soundinternal.h"
+#include "mpg123_decoder.h"
 
 #ifdef HAVE_MPG123
 static bool inited = false;
diff --git a/src/sound/mpg123_decoder.h b/src/sound/mpg123_decoder.h
new file mode 100644
index 000000000..216eae2f9
--- /dev/null
+++ b/src/sound/mpg123_decoder.h
@@ -0,0 +1,48 @@
+#ifndef MPG123_DECODER_H
+#define MPG123_DECODER_H
+
+#include "i_soundinternal.h"
+
+#ifdef HAVE_MPG123
+
+#include "mpg123.h"
+
+struct MPG123Decoder : public SoundDecoder
+{
+    virtual void getInfo(int *samplerate, ChannelConfig *chans, SampleType *type);
+
+    virtual size_t read(char *buffer, size_t bytes);
+    virtual bool seek(size_t ms_offset);
+    virtual size_t getSampleOffset();
+
+    MPG123Decoder() : MPG123(0), File(0) { }
+    virtual ~MPG123Decoder();
+
+protected:
+    virtual bool open(const char *data, size_t length);
+    virtual bool open(const char *fname, size_t offset, size_t length);
+
+private:
+    mpg123_handle *MPG123;
+    bool Done;
+
+    FILE *File;
+    size_t FileLength;
+    size_t FileOffset;
+    static off_t file_lseek(void *handle, off_t offset, int whence);
+    static ssize_t file_read(void *handle, void *buffer, size_t bytes);
+
+    const char *MemData;
+    size_t MemLength;
+    size_t MemPos;
+    static off_t mem_lseek(void *handle, off_t offset, int whence);
+    static ssize_t mem_read(void *handle, void *buffer, size_t bytes);
+
+    // Make non-copyable
+    MPG123Decoder(const MPG123Decoder &rhs);
+    MPG123Decoder& operator=(const MPG123Decoder &rhs);
+};
+
+#endif
+
+#endif /* MPG123_DECODER_H */
diff --git a/src/sound/sndfile_decoder.cpp b/src/sound/sndfile_decoder.cpp
index d90e74abc..534cf343f 100644
--- a/src/sound/sndfile_decoder.cpp
+++ b/src/sound/sndfile_decoder.cpp
@@ -1,4 +1,4 @@
-#include "i_soundinternal.h"
+#include "sndfile_decoder.h"
 
 #ifdef HAVE_SNDFILE
 sf_count_t SndFileDecoder::file_get_filelen(void *user_data)
diff --git a/src/sound/sndfile_decoder.h b/src/sound/sndfile_decoder.h
new file mode 100644
index 000000000..ec59af98f
--- /dev/null
+++ b/src/sound/sndfile_decoder.h
@@ -0,0 +1,55 @@
+#ifndef SNDFILE_DECODER_H
+#define SNDFILE_DECODER_H
+
+#include "i_soundinternal.h"
+
+#ifdef HAVE_SNDFILE
+
+#include "sndfile.h"
+
+struct SndFileDecoder : public SoundDecoder
+{
+    virtual void getInfo(int *samplerate, ChannelConfig *chans, SampleType *type);
+
+    virtual size_t read(char *buffer, size_t bytes);
+    virtual std::vector<char> readAll();
+    virtual bool seek(size_t ms_offset);
+    virtual size_t getSampleOffset();
+
+    SndFileDecoder() : SndFile(0), File(0) { }
+    virtual ~SndFileDecoder();
+
+protected:
+    virtual bool open(const char *data, size_t length);
+    virtual bool open(const char *fname, size_t offset, size_t length);
+
+private:
+    SNDFILE *SndFile;
+    SF_INFO SndInfo;
+
+    FILE *File;
+    size_t FileLength;
+    size_t FileOffset;
+    static sf_count_t file_get_filelen(void *user_data);
+    static sf_count_t file_seek(sf_count_t offset, int whence, void *user_data);
+    static sf_count_t file_read(void *ptr, sf_count_t count, void *user_data);
+    static sf_count_t file_write(const void *ptr, sf_count_t count, void *user_data);
+    static sf_count_t file_tell(void *user_data);
+
+    const char *MemData;
+    size_t MemLength;
+    size_t MemPos;
+    static sf_count_t mem_get_filelen(void *user_data);
+    static sf_count_t mem_seek(sf_count_t offset, int whence, void *user_data);
+    static sf_count_t mem_read(void *ptr, sf_count_t count, void *user_data);
+    static sf_count_t mem_write(const void *ptr, sf_count_t count, void *user_data);
+    static sf_count_t mem_tell(void *user_data);
+
+    // Make non-copyable
+    SndFileDecoder(const SndFileDecoder &rhs);
+    SndFileDecoder& operator=(const SndFileDecoder &rhs);
+};
+
+#endif
+
+#endif /* SNDFILE_DECODER_H */