diff --git a/engine/client/avi/avi_win.c b/engine/client/avi/avi_win.c
index ed1e5ba2..128fe62f 100644
--- a/engine/client/avi/avi_win.c
+++ b/engine/client/avi/avi_win.c
@@ -658,7 +658,7 @@ movie_state_t *AVI_LoadVideo( const char *filename, qboolean load_audio )
 
 	// open cinematic
 	Q_snprintf( path, sizeof( path ), "media/%s", filename );
-	COM_DefaultExtension( path, ".avi" );
+	COM_DefaultExtension( path, ".avi", sizeof( path ));
 	fullpath = FS_GetDiskPath( path, false );
 
 	if( FS_FileExists( path, false ) && !fullpath )
diff --git a/engine/client/cl_gameui.c b/engine/client/cl_gameui.c
index c74932fb..1d3af7ff 100644
--- a/engine/client/cl_gameui.c
+++ b/engine/client/cl_gameui.c
@@ -309,7 +309,7 @@ static void GAME_EXPORT UI_DrawLogo( const char *filename, float x, float y, flo
 
 		// run cinematic if not
 		Q_snprintf( path, sizeof( path ), "media/%s", filename );
-		COM_DefaultExtension( path, ".avi" );
+		COM_DefaultExtension( path, ".avi", sizeof( path ));
 		fullpath = FS_GetDiskPath( path, false );
 
 		if( FS_FileExists( path, false ) && !fullpath )
diff --git a/engine/common/con_utils.c b/engine/common/con_utils.c
index 71995d68..126a289d 100644
--- a/engine/common/con_utils.c
+++ b/engine/common/con_utils.c
@@ -101,8 +101,7 @@ int Cmd_ListMaps( search_t *t, char *lastmapname, size_t len )
 			if( hdrext->id == IDEXTRAHEADER ) version = hdrext->version;
 
 			Q_strncpy( entfilename, t->filenames[i], sizeof( entfilename ));
-			COM_StripExtension( entfilename );
-			COM_DefaultExtension( entfilename, ".ent" );
+			COM_ReplaceExtension( entfilename, ".ent", sizeof( entfilename ));
 			ents = (char *)FS_LoadFile( entfilename, NULL, true );
 
 			if( !ents && lumplen >= 10 )
@@ -925,8 +924,7 @@ qboolean Cmd_CheckMapsList_R( qboolean fRefresh, qboolean onlyingamedir )
 			lumplen = entities.filelen;
 
 			Q_strncpy( entfilename, t->filenames[i], sizeof( entfilename ));
-			COM_StripExtension( entfilename );
-			COM_DefaultExtension( entfilename, ".ent" );
+			COM_ReplaceExtension( entfilename, ".ent", sizeof( entfilename ));
 			ents = (char *)FS_LoadFile( entfilename, NULL, true );
 
 			if( !ents && lumplen >= 10 )
diff --git a/engine/common/host.c b/engine/common/host.c
index d952ddea..ddf488d5 100644
--- a/engine/common/host.c
+++ b/engine/common/host.c
@@ -415,7 +415,7 @@ void Host_Exec_f( void )
 	}
 
 	Q_strncpy( cfgpath, arg, sizeof( cfgpath ));
-	COM_DefaultExtension( cfgpath, ".cfg" ); // append as default
+	COM_DefaultExtension( cfgpath, ".cfg", sizeof( cfgpath )); // append as default
 
 	f = FS_LoadFile( cfgpath, &len, false );
 	if( !f )
diff --git a/engine/common/hpak.c b/engine/common/hpak.c
index 2553f4c5..f7d882d2 100644
--- a/engine/common/hpak.c
+++ b/engine/common/hpak.c
@@ -109,7 +109,7 @@ void HPAK_CreatePak( const char *filename, resource_t *pResource, byte *pData, f
 		return;
 
 	Q_strncpy( pakname, filename, sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 
 	Con_Printf( "creating HPAK %s.\n", pakname );
 
@@ -257,7 +257,7 @@ void HPAK_AddLump( qboolean bUseQueue, const char *name, resource_t *pResource,
 	}
 
 	Q_strncpy( srcname, name, sizeof( srcname ));
-	COM_ReplaceExtension( srcname, ".hpk" );
+	COM_ReplaceExtension( srcname, ".hpk", sizeof( srcname ));
 
 	file_src = FS_Open( srcname, "rb", true );
 
@@ -269,7 +269,7 @@ void HPAK_AddLump( qboolean bUseQueue, const char *name, resource_t *pResource,
 	}
 
 	Q_strncpy( dstname, srcname, sizeof( dstname ));
-	COM_ReplaceExtension( dstname, ".hp2" );
+	COM_ReplaceExtension( dstname, ".hp2", sizeof( dstname ));
 
 	file_dst = FS_Open( dstname, "wb", true );
 
@@ -395,7 +395,7 @@ static qboolean HPAK_Validate( const char *filename, qboolean quiet, qboolean de
 		return true;
 
 	Q_strncpy( pakname, filename, sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 
 	f = FS_Open( pakname, "rb", true );
 	if( !f )
@@ -497,7 +497,7 @@ void HPAK_CheckIntegrity( const char *filename )
 		return;
 
 	Q_strncpy( pakname, filename, sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 
 	HPAK_Validate( pakname, true, true );
 }
@@ -514,7 +514,7 @@ void HPAK_CheckSize( const char *filename )
 		return;
 
 	Q_strncpy( pakname, filename, sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 
 	if( FS_FileSize( pakname, false ) > ( maxsize * 1048576 ))
 	{
@@ -547,7 +547,7 @@ qboolean HPAK_ResourceForHash( const char *filename, byte *hash, resource_t *pRe
 	}
 
 	Q_strncpy( pakname, filename, sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 
 	f = FS_Open( pakname, "rb", true );
 	if( !f ) return false;
@@ -595,7 +595,7 @@ static qboolean HPAK_ResourceForIndex( const char *filename, int index, resource
 		return false;
 
 	Q_strncpy( pakname, filename, sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 
 	f = FS_Open( pakname, "rb", true );
 	if( !f )
@@ -681,7 +681,7 @@ qboolean HPAK_GetDataPointer( const char *filename, resource_t *pResource, byte
 	}
 
 	Q_strncpy( pakname, filename, sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 
 	f = FS_Open( pakname, "rb", true );
 	if( !f ) return false;
@@ -764,7 +764,7 @@ void HPAK_RemoveLump( const char *name, resource_t *pResource )
 	HPAK_FlushHostQueue();
 
 	Q_strncpy( read_path, name, sizeof( read_path ));
-	COM_ReplaceExtension( read_path, ".hpk" );
+	COM_ReplaceExtension( read_path, ".hpk", sizeof( read_path ));
 
 	file_src = FS_Open( read_path, "rb", true );
 	if( !file_src )
@@ -774,7 +774,7 @@ void HPAK_RemoveLump( const char *name, resource_t *pResource )
 	}
 
 	Q_strncpy( save_path, read_path, sizeof( save_path ));
-	COM_ReplaceExtension( save_path, ".hp2" );
+	COM_ReplaceExtension( save_path, ".hp2", sizeof( save_path ));
 	file_dst = FS_Open( save_path, "wb", true );
 
 	if( !file_dst )
@@ -893,7 +893,7 @@ void HPAK_List_f( void )
 	HPAK_FlushHostQueue();
 
 	Q_strncpy( pakname, Cmd_Argv( 1 ), sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 	Con_Printf( "Contents for %s.\n", pakname );
 
 	f = FS_Open( pakname, "rb", true );
@@ -984,7 +984,7 @@ void HPAK_Extract_f( void )
 	HPAK_FlushHostQueue();
 
 	Q_strncpy( pakname, Cmd_Argv( 1 ), sizeof( pakname ));
-	COM_ReplaceExtension( pakname, ".hpk" );
+	COM_ReplaceExtension( pakname, ".hpk", sizeof( pakname ));
 	Con_Printf( "Contents for %s.\n", pakname );
 
 	f = FS_Open( pakname, "rb", true );
diff --git a/engine/common/mod_bmodel.c b/engine/common/mod_bmodel.c
index f2a1b466..8c63462c 100644
--- a/engine/common/mod_bmodel.c
+++ b/engine/common/mod_bmodel.c
@@ -1764,7 +1764,7 @@ static void Mod_LoadEntities( dbspmodel_t *bmod )
 
 		// world is check for entfile too
 		Q_strncpy( entfilename, loadmodel->name, sizeof( entfilename ));
-		COM_ReplaceExtension( entfilename, ".ent" );
+		COM_ReplaceExtension( entfilename, ".ent", sizeof( entfilename ));
 
 		// make sure what entity patch is never than bsp
 		ft1 = FS_FileTime( loadmodel->name, false );
diff --git a/engine/common/net_chan.c b/engine/common/net_chan.c
index 9e4a06a2..aec27f75 100644
--- a/engine/common/net_chan.c
+++ b/engine/common/net_chan.c
@@ -973,7 +973,7 @@ int Netchan_CreateFileFragments( netchan_t *chan, const char *filename )
 	else chunksize = FRAGMENT_MAX_SIZE; // fallback
 
 	Q_strncpy( compressedfilename, filename, sizeof( compressedfilename ));
-	COM_ReplaceExtension( compressedfilename, ".ztmp" );
+	COM_ReplaceExtension( compressedfilename, ".ztmp", sizeof( compressedfilename ));
 	compressedFileTime = FS_FileTime( compressedfilename, false );
 	fileTime = FS_FileTime( filename, false );
 
@@ -1559,7 +1559,7 @@ void Netchan_TransmitBits( netchan_t *chan, int length, byte *data )
 						char	compressedfilename[MAX_OSPATH];
 
 						Q_strncpy( compressedfilename, pbuf->filename, sizeof( compressedfilename ));
-						COM_ReplaceExtension( compressedfilename, ".ztmp" );
+						COM_ReplaceExtension( compressedfilename, ".ztmp", sizeof( compressedfilename ));
 						file = FS_Open( compressedfilename, "rb", false );
 					}
 					else file = FS_Open( pbuf->filename, "rb", false );
diff --git a/engine/platform/sdl/vid_sdl.c b/engine/platform/sdl/vid_sdl.c
index cf0d697f..b791cc6c 100644
--- a/engine/platform/sdl/vid_sdl.c
+++ b/engine/platform/sdl/vid_sdl.c
@@ -736,9 +736,8 @@ qboolean VID_CreateWindow( int width, int height, qboolean fullscreen )
 
 	if( !iconLoaded )
 	{
-		Q_strcpy( iconpath, GI->iconpath );
-		COM_StripExtension( iconpath );
-		COM_DefaultExtension( iconpath, ".tga" );
+		Q_strncpy( iconpath, GI->iconpath, sizeof( iconpath ));
+		COM_ReplaceExtension( iconpath, ".tga", sizeof( iconpath ));
 
 		icon = FS_LoadImage( iconpath, NULL, 0 );
 
diff --git a/engine/server/sv_init.c b/engine/server/sv_init.c
index 12e07a61..a5391168 100644
--- a/engine/server/sv_init.c
+++ b/engine/server/sv_init.c
@@ -340,7 +340,7 @@ void SV_CreateGenericResources( void )
 	string	filename;
 
 	Q_strncpy( filename, sv.model_precache[1], sizeof( filename ));
-	COM_ReplaceExtension( filename, ".res" );
+	COM_ReplaceExtension( filename, ".res", sizeof( filename ));
 	COM_FixSlashes( filename );
 
 	SV_ReadResourceList( filename );