diff --git a/dlls/avifil32/avifile_private.h b/dlls/avifil32/avifile_private.h
index 85f1ca140c..d35aa0f857 100644
--- a/dlls/avifil32/avifile_private.h
+++ b/dlls/avifil32/avifile_private.h
@@ -57,16 +57,16 @@ DEFINE_AVIGUID(CLSID_ICMStream, 0x00020001, 0, 0);
 DEFINE_AVIGUID(CLSID_WAVFile,   0x00020003, 0, 0);
 DEFINE_AVIGUID(CLSID_ACMStream, 0x0002000F, 0, 0);
 
-extern HMODULE AVIFILE_hModule;
+extern HMODULE AVIFILE_hModule DECLSPEC_HIDDEN;
 
-extern HRESULT AVIFILE_CreateAVIFile(REFIID riid, LPVOID *ppobj);
-extern HRESULT AVIFILE_CreateWAVFile(REFIID riid, LPVOID *ppobj);
-extern HRESULT AVIFILE_CreateACMStream(REFIID riid, LPVOID *ppobj);
-extern HRESULT AVIFILE_CreateICMStream(REFIID riid, LPVOID *ppobj);
-extern PAVIEDITSTREAM AVIFILE_CreateEditStream(PAVISTREAM pstream);
-extern PGETFRAME AVIFILE_CreateGetFrame(PAVISTREAM pstream);
-extern PAVIFILE  AVIFILE_CreateAVITempFile(int nStreams, const PAVISTREAM *ppStreams);
+extern HRESULT AVIFILE_CreateAVIFile(REFIID riid, LPVOID *ppobj) DECLSPEC_HIDDEN;
+extern HRESULT AVIFILE_CreateWAVFile(REFIID riid, LPVOID *ppobj) DECLSPEC_HIDDEN;
+extern HRESULT AVIFILE_CreateACMStream(REFIID riid, LPVOID *ppobj) DECLSPEC_HIDDEN;
+extern HRESULT AVIFILE_CreateICMStream(REFIID riid, LPVOID *ppobj) DECLSPEC_HIDDEN;
+extern PAVIEDITSTREAM AVIFILE_CreateEditStream(PAVISTREAM pstream) DECLSPEC_HIDDEN;
+extern PGETFRAME AVIFILE_CreateGetFrame(PAVISTREAM pstream) DECLSPEC_HIDDEN;
+extern PAVIFILE  AVIFILE_CreateAVITempFile(int nStreams, const PAVISTREAM *ppStreams) DECLSPEC_HIDDEN;
 
-extern LPCWSTR  AVIFILE_BasenameW(LPCWSTR szFileName);
+extern LPCWSTR  AVIFILE_BasenameW(LPCWSTR szFileName) DECLSPEC_HIDDEN;
 
 #endif
diff --git a/dlls/avifil32/extrachunk.h b/dlls/avifil32/extrachunk.h
index 1eda7ef33c..843a73c7b5 100644
--- a/dlls/avifil32/extrachunk.h
+++ b/dlls/avifil32/extrachunk.h
@@ -35,18 +35,18 @@ typedef struct _EXTRACHUNKS {
 } EXTRACHUNKS, *LPEXTRACHUNKS;
 
 /* reads a chunk outof the extrachunk-structure */
-HRESULT ReadExtraChunk(const EXTRACHUNKS *extra,FOURCC ckid,LPVOID lp,LPLONG size);
+HRESULT ReadExtraChunk(const EXTRACHUNKS *extra,FOURCC ckid,LPVOID lp,LPLONG size) DECLSPEC_HIDDEN;
 
 /* writes a chunk into the extrachunk-structure */
-HRESULT WriteExtraChunk(LPEXTRACHUNKS extra,FOURCC ckid,LPCVOID lp,LONG size);
+HRESULT WriteExtraChunk(LPEXTRACHUNKS extra,FOURCC ckid,LPCVOID lp,LONG size) DECLSPEC_HIDDEN;
 
 /* reads a chunk fomr the HMMIO into the extrachunk-structure */
-HRESULT ReadChunkIntoExtra(LPEXTRACHUNKS extra,HMMIO hmmio,const MMCKINFO *lpck);
+HRESULT ReadChunkIntoExtra(LPEXTRACHUNKS extra,HMMIO hmmio,const MMCKINFO *lpck) DECLSPEC_HIDDEN;
 
 /* reads all non-junk chunks into the extrachunk-structure until it finds
  * the given chunk or the optional parent-chunk is at the end */
 HRESULT FindChunkAndKeepExtras(LPEXTRACHUNKS extra,HMMIO hmmio,
-			       MMCKINFO *lpck,MMCKINFO *lpckParent,UINT flags);
+			       MMCKINFO *lpck,MMCKINFO *lpckParent,UINT flags) DECLSPEC_HIDDEN;
 
 #ifdef __cplusplus
 }