diff --git a/src/company_cmd.cpp b/src/company_cmd.cpp
--- a/src/company_cmd.cpp
+++ b/src/company_cmd.cpp
@@ -138,7 +138,7 @@ void DrawCompanyIcon(CompanyID c, int x,
  * @param cmf the fact to check
  * @return true if and only if the face is valid
  */
-bool IsValidCompanyManagerFace(CompanyManagerFace cmf)
+static bool IsValidCompanyManagerFace(CompanyManagerFace cmf)
 {
 	if (!AreCompanyManagerFaceBitsValid(cmf, CMFV_GEN_ETHN, GE_WM)) return false;
 
diff --git a/src/company_manager_face.h b/src/company_manager_face.h
--- a/src/company_manager_face.h
+++ b/src/company_manager_face.h
@@ -237,6 +237,5 @@ static inline SpriteID GetCompanyManager
 }
 
 void DrawCompanyManagerFace(CompanyManagerFace face, int colour, int x, int y);
-bool IsValidCompanyManagerFace(CompanyManagerFace cmf);
 
 #endif /* COMPANY_MANAGER_FACE_H */
diff --git a/src/fileio.cpp b/src/fileio.cpp
--- a/src/fileio.cpp
+++ b/src/fileio.cpp
@@ -426,7 +426,7 @@ FILE *FioFOpenFile(const char *filename,
  * Create a directory with the given name
  * @param name the new name of the directory
  */
-void FioCreateDirectory(const char *name)
+static void FioCreateDirectory(const char *name)
 {
 #if defined(WIN32) || defined(WINCE)
 	CreateDirectory(OTTD2FS(name), NULL);
diff --git a/src/fileio_func.h b/src/fileio_func.h
--- a/src/fileio_func.h
+++ b/src/fileio_func.h
@@ -25,7 +25,6 @@ void FioCloseAll();
 void FioOpenFile(int slot, const char *filename);
 void FioReadBlock(void *ptr, size_t size);
 void FioSkipBytes(int n);
-void FioCreateDirectory(const char *filename);
 
 /**
  * The searchpaths OpenTTD could search through.
diff --git a/src/network/network_func.h b/src/network/network_func.h
--- a/src/network/network_func.h
+++ b/src/network/network_func.h
@@ -72,7 +72,6 @@ const char *GetClientIP(NetworkClientInf
 
 void NetworkServerDoMove(ClientID client_id, CompanyID company_id);
 void NetworkServerSendRcon(ClientID client_id, ConsoleColour colour_code, const char *string);
-void NetworkServerSendError(ClientID client_id, NetworkErrorCode error);
 void NetworkServerSendChat(NetworkAction action, DestType type, int dest, const char *msg, ClientID from_id, int64 data = 0);
 
 void NetworkServerKickClient(ClientID client_id);
diff --git a/src/network/network_server.cpp b/src/network/network_server.cpp
--- a/src/network/network_server.cpp
+++ b/src/network/network_server.cpp
@@ -1776,7 +1776,7 @@ void NetworkServerSendRcon(ClientID clie
 	SEND_COMMAND(PACKET_SERVER_RCON)(NetworkFindClientStateFromClientID(client_id), colour_code, string);
 }
 
-void NetworkServerSendError(ClientID client_id, NetworkErrorCode error)
+static void NetworkServerSendError(ClientID client_id, NetworkErrorCode error)
 {
 	SEND_COMMAND(PACKET_SERVER_ERROR)(NetworkFindClientStateFromClientID(client_id), error);
 }
diff --git a/src/newgrf_canal.cpp b/src/newgrf_canal.cpp
--- a/src/newgrf_canal.cpp
+++ b/src/newgrf_canal.cpp
@@ -114,7 +114,7 @@ SpriteID GetCanalSprite(CanalFeature fea
  * @param tile     Tile index of canal.
  * @return Callback result or CALLBACK_FAILED if the callback failed.
  */
-uint16 GetCanalCallback(CallbackID callback, uint32 param1, uint32 param2, CanalFeature feature, TileIndex tile)
+static uint16 GetCanalCallback(CallbackID callback, uint32 param1, uint32 param2, CanalFeature feature, TileIndex tile)
 {
 	ResolverObject object;
 	const SpriteGroup *group;
diff --git a/src/newgrf_canal.h b/src/newgrf_canal.h
--- a/src/newgrf_canal.h
+++ b/src/newgrf_canal.h
@@ -58,7 +58,6 @@ extern WaterFeature _water_feature[CF_EN
  */
 SpriteID GetCanalSprite(CanalFeature feature, TileIndex tile);
 
-uint16 GetCanalCallback(CallbackID callback, uint32 param1, uint32 param2, CanalFeature feature, TileIndex tile);
 uint GetCanalSpriteOffset(CanalFeature feature, TileIndex tile, uint cur_offset);
 
 #endif /* NEWGRF_CANAL_H */
diff --git a/src/settings.cpp b/src/settings.cpp
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -161,7 +161,7 @@ static uint32 LookupManyOfMany(const cha
  * @param maxitems the maximum number of elements the integerlist-array has
  * @return returns the number of items found, or -1 on an error
  */
-int ParseIntList(const char *p, int *items, int maxitems)
+static int ParseIntList(const char *p, int *items, int maxitems)
 {
 	int n = 0; // number of items read so far
 	bool comma = false; // do we accept comma?
diff --git a/src/settings_func.h b/src/settings_func.h
--- a/src/settings_func.h
+++ b/src/settings_func.h
@@ -20,8 +20,6 @@ void IConsoleSetSetting(const char *name
 void IConsoleGetSetting(const char *name, bool force_newgame = false);
 void IConsoleListSettings(const char *prefilter);
 
-int ParseIntList(const char *p, int *items, int maxitems);
-
 void LoadFromConfig();
 void SaveToConfig();
 void CheckConfig();
diff --git a/src/window.cpp b/src/window.cpp
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -145,7 +145,7 @@ void SetFocusedWindow(Window *w)
  * has a edit box as focused widget, or if a console is focused.
  * @return returns true if an edit box is in global focus or if the focused window is a console, else false
  */
-bool EditBoxInGlobalFocus()
+static bool EditBoxInGlobalFocus()
 {
 	if (_focused_window == NULL) return false;
 
diff --git a/src/window_gui.h b/src/window_gui.h
--- a/src/window_gui.h
+++ b/src/window_gui.h
@@ -815,7 +815,6 @@ extern SpecialMouseMode _special_mouse_m
 Window *GetCallbackWnd();
 
 void SetFocusedWindow(Window *w);
-bool EditBoxInGlobalFocus();
 
 void ScrollbarClickHandler(Window *w, NWidgetCore *nw, int x, int y);