diff --git a/src/common/range.h b/src/common/range.h
index ed06958f..9f508202 100644
--- a/src/common/range.h
+++ b/src/common/range.h
@@ -19,6 +19,8 @@ public:
 	void setMin(int min) {_min = min;}
 	void setMax(int max) {_max = max;}
 
+	bool contains(int val) const {return (val >= _min && val <= _max);}
+
 private:
 	int _min, _max;
 };
diff --git a/src/common/rectc.h b/src/common/rectc.h
index fe1a54d1..f034167c 100644
--- a/src/common/rectc.h
+++ b/src/common/rectc.h
@@ -23,6 +23,11 @@ public:
 	  {return Coordinates((_tl.lon() + _br.lon()) / 2.0,
 	    (_tl.lat() + _br.lat()) / 2.0);}
 
+	double top() const {return _tl.lat();}
+	double bottom() const {return _br.lat();}
+	double left() const {return _tl.lon();}
+	double right() const {return _br.lon();}
+
 	RectC operator|(const RectC &r) const;
 	RectC &operator|=(const RectC &r) {*this = *this | r; return *this;}
 	RectC operator&(const RectC &r) const;
diff --git a/src/map/mapsource.cpp b/src/map/mapsource.cpp
index 4f0cf81d..5469677a 100644
--- a/src/map/mapsource.cpp
+++ b/src/map/mapsource.cpp
@@ -4,19 +4,12 @@
 #include "onlinemap.h"
 #include "wmtsmap.h"
 #include "wmsmap.h"
+#include "osm.h"
 #include "mapsource.h"
 
-#define ZOOM_MAX       19
-#define ZOOM_MIN       0
-#define BOUNDS_LEFT    -180
-#define BOUNDS_TOP     85.0511
-#define BOUNDS_RIGHT   180
-#define BOUNDS_BOTTOM  -85.0511
 
-
-MapSource::Config::Config() : type(OSM), zooms(ZOOM_MIN, ZOOM_MAX),
-  bounds(Coordinates(BOUNDS_LEFT, BOUNDS_TOP), Coordinates(BOUNDS_RIGHT,
-  BOUNDS_BOTTOM)), format("image/png"), rest(false), tileRatio(1.0) {}
+MapSource::Config::Config() : type(OSM), zooms(osm::zooms), bounds(osm::bounds),
+  format("image/png"), rest(false), tileRatio(1.0) {}
 
 
 static CoordinateSystem coordinateSystem(QXmlStreamReader &reader)
@@ -38,21 +31,21 @@ Range MapSource::zooms(QXmlStreamReader &reader)
 
 	if (attr.hasAttribute("min")) {
 		min = attr.value("min").toString().toInt(&res);
-		if (!res || (min < ZOOM_MIN || min > ZOOM_MAX)) {
+		if (!res || !osm::zooms.contains(min)) {
 			reader.raiseError("Invalid minimal zoom level");
 			return Range();
 		}
 	} else
-		min = ZOOM_MIN;
+		min = osm::zooms.min();
 
 	if (attr.hasAttribute("max")) {
 		max = attr.value("max").toString().toInt(&res);
-		if (!res || (max < ZOOM_MIN || max > ZOOM_MAX)) {
+		if (!res || !osm::zooms.contains(max)) {
 			reader.raiseError("Invalid maximal zoom level");
 			return Range();
 		}
 	} else
-		max = ZOOM_MAX;
+		max = osm::zooms.max();
 
 	if (min > max) {
 		reader.raiseError("Invalid maximal/minimal zoom level combination");
@@ -70,39 +63,41 @@ RectC MapSource::bounds(QXmlStreamReader &reader)
 
 	if (attr.hasAttribute("top")) {
 		top = attr.value("top").toString().toDouble(&res);
-		if (!res || (top < BOUNDS_BOTTOM || top > BOUNDS_TOP)) {
+		if (!res || (top < osm::bounds.bottom() || top > osm::bounds.top())) {
 			reader.raiseError("Invalid bounds top value");
 			return RectC();
 		}
 	} else
-		top = BOUNDS_TOP;
+		top = osm::bounds.top();
 
 	if (attr.hasAttribute("bottom")) {
 		bottom = attr.value("bottom").toString().toDouble(&res);
-		if (!res || (bottom < BOUNDS_BOTTOM || bottom > BOUNDS_TOP)) {
+		if (!res || (bottom < osm::bounds.bottom()
+		  || bottom > osm::bounds.top())) {
 			reader.raiseError("Invalid bounds bottom value");
 			return RectC();
 		}
 	} else
-		bottom = BOUNDS_BOTTOM;
+		bottom = osm::bounds.bottom();
 
 	if (attr.hasAttribute("left")) {
 		left = attr.value("left").toString().toDouble(&res);
-		if (!res || (left < BOUNDS_LEFT || left > BOUNDS_RIGHT)) {
+		if (!res || (left < osm::bounds.left() || left > osm::bounds.right())) {
 			reader.raiseError("Invalid bounds left value");
 			return RectC();
 		}
 	} else
-		left = BOUNDS_LEFT;
+		left = osm::bounds.left();
 
 	if (attr.hasAttribute("right")) {
 		right = attr.value("right").toString().toDouble(&res);
-		if (!res || (right < BOUNDS_LEFT || right > BOUNDS_RIGHT)) {
+		if (!res || (right < osm::bounds.left()
+		  || right > osm::bounds.right())) {
 			reader.raiseError("Invalid bounds right value");
 			return RectC();
 		}
 	} else
-		right = BOUNDS_RIGHT;
+		right = osm::bounds.right();
 
 	if (bottom >= top) {
 		reader.raiseError("Invalid bottom/top bounds combination");
diff --git a/src/map/mbtilesmap.cpp b/src/map/mbtilesmap.cpp
index 795b34b0..01b439c1 100644
--- a/src/map/mbtilesmap.cpp
+++ b/src/map/mbtilesmap.cpp
@@ -77,8 +77,8 @@ MBTilesMap::MBTilesMap(const QString &fileName, QObject *parent)
 		Coordinates tl(osm::m2ll(QPointF(minX, maxY)));
 		Coordinates br(osm::m2ll(QPointF(maxX, minY)));
 		// Workaround of broken zoom levels 0 and 1 due to numerical instability
-		tl.rlat() = qMin(tl.lat(), 85.0511);
-		br.rlat() = qMax(br.lat(), -85.0511);
+		tl.rlat() = qMin(tl.lat(), osm::bounds.top());
+		br.rlat() = qMax(br.lat(), osm::bounds.bottom());
 		_bounds = RectC(tl, br);
 	}
 
diff --git a/src/map/osm.h b/src/map/osm.h
index e93c19a8..a9f79183 100644
--- a/src/map/osm.h
+++ b/src/map/osm.h
@@ -3,9 +3,15 @@
 
 #include <QPointF>
 #include <common/coordinates.h>
+#include <common/rectc.h>
+#include <common/range.h>
 
 namespace osm
 {
+	static const RectC bounds(Coordinates(-180, 85.0511),
+	  Coordinates(180, -85.0511));
+	static const Range zooms(0, 19);
+
 	QPointF ll2m(const Coordinates &c);
 	Coordinates m2ll(const QPointF &p);
 	QPoint mercator2tile(const QPointF &m, int z);