diff --git Makefile Makefile
index 250a5e0cd..cb008b613 100644
--- Makefile
+++ Makefile
@@ -196,7 +196,7 @@ ifdef WITH_REVISION
   endif
 endif
 
-CFLAGS   += -Wall -W -Wcast-qual -Wpointer-arith -Wcast-align $(FLAGS)
+CFLAGS   += -Wall -Wextra -Wcast-qual -Wpointer-arith -Wcast-align $(FLAGS)
 CCFLAGS  += -ansi -Wstrict-prototypes -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64
 
 
diff --git dataobj/crossing_logic.cc dataobj/crossing_logic.cc
index 1b2f008e0..a6a1be795 100644
--- dataobj/crossing_logic.cc
+++ dataobj/crossing_logic.cc
@@ -206,8 +206,8 @@ int compare_crossing(const crossing_desc_t *c0, const crossing_desc_t *c1)
 void crossing_logic_t::register_desc(crossing_desc_t *desc)
 {
 	// mark if crossing possible
-	const waytype_t way0 = (const waytype_t)min(desc->get_waytype(0), desc->get_waytype(1));
-	const waytype_t way1 = (const waytype_t)max(desc->get_waytype(0), desc->get_waytype(1));
+	const waytype_t way0 = (waytype_t)min(desc->get_waytype(0), desc->get_waytype(1));
+	const waytype_t way1 = (waytype_t)max(desc->get_waytype(0), desc->get_waytype(1));
 	if(way0<8  &&  way1<9  &&  way0<way1) {
 		uint8 index = way0 * 9 + way1 - ((way0+2)*(way0+1))/2;
 		// max index = 7*9 + 8 - 9*4 = 71-36 = 35
diff --git dataobj/route.cc dataobj/route.cc
index 6f84e2d0d..d5a77378f 100644
--- dataobj/route.cc
+++ dataobj/route.cc
@@ -534,7 +534,9 @@ bool route_t::intern_calc_route(karte_t *welt, const koord3d ziel, const koord3d
 		}
 	}
 	else {
+#ifdef DEBUG
 		uint32 best = tmp->g;
+#endif
 		// reached => construct route
 		route.store_at( tmp->count, tmp->gr->get_pos() );
 		while(tmp != NULL) {
diff --git gui/welt.cc gui/welt.cc
index 939f1be35..2e85b71a9 100644
--- gui/welt.cc
+++ gui/welt.cc
@@ -393,11 +393,11 @@ void welt_gui_t::resize_preview()
 
 	if(  world_aspect > 1.0  ) {
 		map_size.w = MAP_PREVIEW_SIZE_X-2;
-		map_size.h = (sint16) max( (const int)((float)map_size.w / world_aspect), L_PREVIEW_SIZE_MIN-2);
+		map_size.h = (sint16) max( (int)((float)map_size.w / world_aspect), L_PREVIEW_SIZE_MIN-2);
 	}
 	else {
 		map_size.h = MAP_PREVIEW_SIZE_Y-2;
-		map_size.w = (sint16) max( (const int)((float)map_size.h * world_aspect), L_PREVIEW_SIZE_MIN-2);
+		map_size.w = (sint16) max( (int)((float)map_size.h * world_aspect), L_PREVIEW_SIZE_MIN-2);
 	}
 	map.resize( map_size.w, map_size.h );
 }
diff --git simmem.h simmem.h
index 9d720487f..358b2e5c4 100644
--- simmem.h
+++ simmem.h
@@ -18,6 +18,6 @@ void* xrealloc(void * const ptr, size_t size); // Throws std::bad_alloc on failu
 #define MALLOCN(type, n)         ((type*)xmalloc(sizeof(type) * (n))) // Allocate n objects of a certain type
 #define MALLOCF(type, member, n) ((type*)xmalloc(offsetof(type, member) + sizeof(*((type*)0)->member) * (n)))
 
-#define REALLOC(ptr, type, n) (type*)xrealloc((void * const)ptr, sizeof(type) * (n)) // Reallocate n objects of a certain type
+#define REALLOC(ptr, type, n) (type*)xrealloc((void *)ptr, sizeof(type) * (n)) // Reallocate n objects of a certain type
 
 #endif
diff --git vehicle/simpeople.cc vehicle/simpeople.cc
index 4f6ef51e2..266649f93 100644
--- vehicle/simpeople.cc
+++ vehicle/simpeople.cc
@@ -322,7 +322,7 @@ void pedestrian_t::get_screen_offset( int &xoff, int &yoff, const sint16 raster_
 {
 	// vehicles needs finer steps to appear smoother
 	sint32 display_steps = (uint32)(steps + steps_offset)*(uint16)raster_width;
-	if(dx*dy) {
+	if(  dx && dy  ) {
 		display_steps &= 0xFFFFFC00;
 	}
 	else {
diff --git vehicle/simvehicle.cc vehicle/simvehicle.cc
index a6b3e99b0..79bf76cfe 100644
--- vehicle/simvehicle.cc
+++ vehicle/simvehicle.cc
@@ -530,7 +530,7 @@ sint16 vehicle_base_t::get_hoff(const sint16 raster_width) const
 vehicle_base_t *vehicle_base_t::no_cars_blocking( const grund_t *gr, const convoi_t *cnv, const uint8 current_direction, const uint8 next_direction, const uint8 next_90direction )
 {
 	// Search vehicle
-	for(  uint8 pos=1;  pos<(volatile uint8)gr->get_top();  pos++  ) {
+	for(  uint8 pos=1;  pos<(uint8)gr->get_top();  pos++  ) {
 		if(  vehicle_base_t* const v = obj_cast<vehicle_base_t>(gr->obj_bei(pos))  ) {
 			if(  v->get_typ()==obj_t::pedestrian  ) {
 				continue;