diff --git a/src/ol/style/fillsymbolizer.js b/src/ol/style/fillsymbolizer.js
index 603aa34a5a..b5e079117e 100644
--- a/src/ol/style/fillsymbolizer.js
+++ b/src/ol/style/fillsymbolizer.js
@@ -64,9 +64,8 @@ ol.style.Fill.prototype.createLiteral = function(featureOrType) {
     goog.asserts.assertString(
         color, 'color must be a string');
 
-    var opacity = ol.expr.evaluateFeature(this.opacity_, feature);
-    goog.asserts.assertNumber(
-        opacity, 'color must be a number');
+    var opacity = Number(ol.expr.evaluateFeature(this.opacity_, feature));
+    goog.asserts.assert(!isNaN(opacity), 'opacity must be a number');
 
     literal = new ol.style.PolygonLiteral({
       fillColor: color,
diff --git a/src/ol/style/iconsymbolizer.js b/src/ol/style/iconsymbolizer.js
index c112f341de..781c6eb73d 100644
--- a/src/ol/style/iconsymbolizer.js
+++ b/src/ol/style/iconsymbolizer.js
@@ -90,21 +90,21 @@ ol.style.Icon.prototype.createLiteral = function(featureOrType) {
 
     var width;
     if (!goog.isNull(this.width_)) {
-      width = ol.expr.evaluateFeature(this.width_, feature);
-      goog.asserts.assertNumber(width, 'width must be a number');
+      width = Number(ol.expr.evaluateFeature(this.width_, feature));
+      goog.asserts.assert(!isNaN(width), 'width must be a number');
     }
 
     var height;
     if (!goog.isNull(this.height_)) {
-      height = ol.expr.evaluateFeature(this.height_, feature);
+      height = Number(ol.expr.evaluateFeature(this.height_, feature));
       goog.asserts.assertNumber(height, 'height must be a number');
     }
 
-    var opacity = ol.expr.evaluateFeature(this.opacity_, feature);
-    goog.asserts.assertNumber(opacity, 'opacity must be a number');
+    var opacity = Number(ol.expr.evaluateFeature(this.opacity_, feature));
+    goog.asserts.assert(!isNaN(opacity), 'opacity must be a number');
 
-    var rotation = ol.expr.evaluateFeature(this.rotation_, feature);
-    goog.asserts.assertNumber(rotation, 'rotation must be a number');
+    var rotation = Number(ol.expr.evaluateFeature(this.rotation_, feature));
+    goog.asserts.assert(!isNaN(rotation), 'rotation must be a number');
 
     literal = new ol.style.IconLiteral({
       url: url,
diff --git a/src/ol/style/shapesymbolizer.js b/src/ol/style/shapesymbolizer.js
index 29281bb002..2e7b00fd1c 100644
--- a/src/ol/style/shapesymbolizer.js
+++ b/src/ol/style/shapesymbolizer.js
@@ -73,17 +73,17 @@ ol.style.Shape.prototype.createLiteral = function(featureOrType) {
   var literal = null;
   if (type === ol.geom.GeometryType.POINT ||
       type === ol.geom.GeometryType.MULTIPOINT) {
-    var size = ol.expr.evaluateFeature(this.size_, feature);
-    goog.asserts.assertNumber(size, 'size must be a number');
+    var size = Number(ol.expr.evaluateFeature(this.size_, feature));
+    goog.asserts.assert(!isNaN(size), 'size must be a number');
 
     var fillColor, fillOpacity;
     if (!goog.isNull(this.fill_)) {
       fillColor = ol.expr.evaluateFeature(this.fill_.getColor(), feature);
       goog.asserts.assertString(
           fillColor, 'fillColor must be a string');
-      fillOpacity = ol.expr.evaluateFeature(this.fill_.getOpacity(), feature);
-      goog.asserts.assertNumber(
-          fillOpacity, 'fillOpacity must be a number');
+      fillOpacity = Number(ol.expr.evaluateFeature(
+          this.fill_.getOpacity(), feature));
+      goog.asserts.assert(!isNaN(fillOpacity), 'fillOpacity must be a number');
     }
 
     var strokeColor, strokeOpacity, strokeWidth;
@@ -91,13 +91,13 @@ ol.style.Shape.prototype.createLiteral = function(featureOrType) {
       strokeColor = ol.expr.evaluateFeature(this.stroke_.getColor(), feature);
       goog.asserts.assertString(
           strokeColor, 'strokeColor must be a string');
-      strokeOpacity = ol.expr.evaluateFeature(this.stroke_.getOpacity(),
-          feature);
-      goog.asserts.assertNumber(
-          strokeOpacity, 'strokeOpacity must be a number');
-      strokeWidth = ol.expr.evaluateFeature(this.stroke_.getWidth(), feature);
-      goog.asserts.assertNumber(
-          strokeWidth, 'strokeWidth must be a number');
+      strokeOpacity = Number(ol.expr.evaluateFeature(
+          this.stroke_.getOpacity(), feature));
+      goog.asserts.assert(!isNaN(strokeOpacity),
+          'strokeOpacity must be a number');
+      strokeWidth = Number(ol.expr.evaluateFeature(
+          this.stroke_.getWidth(), feature));
+      goog.asserts.assert(!isNaN(strokeWidth), 'strokeWidth must be a number');
     }
 
     literal = new ol.style.ShapeLiteral({
diff --git a/src/ol/style/strokesymbolizer.js b/src/ol/style/strokesymbolizer.js
index ef14a01f54..f1f0b389aa 100644
--- a/src/ol/style/strokesymbolizer.js
+++ b/src/ol/style/strokesymbolizer.js
@@ -71,13 +71,13 @@ ol.style.Stroke.prototype.createLiteral = function(featureOrType) {
       this.color_, feature);
   goog.asserts.assertString(color, 'color must be a string');
 
-  var opacity = ol.expr.evaluateFeature(
-      this.opacity_, feature);
-  goog.asserts.assertNumber(opacity, 'opacity must be a number');
+  var opacity = Number(ol.expr.evaluateFeature(
+      this.opacity_, feature));
+  goog.asserts.assert(!isNaN(opacity), 'opacity must be a number');
 
-  var width = ol.expr.evaluateFeature(
-      this.width_, feature);
-  goog.asserts.assertNumber(width, 'width must be a number');
+  var width = Number(ol.expr.evaluateFeature(
+      this.width_, feature));
+  goog.asserts.assert(!isNaN(width), 'width must be a number');
 
   var literal = null;
   if (type === ol.geom.GeometryType.LINESTRING ||
diff --git a/src/ol/style/textsymbolizer.js b/src/ol/style/textsymbolizer.js
index 9cc4d9bb83..39230ed944 100644
--- a/src/ol/style/textsymbolizer.js
+++ b/src/ol/style/textsymbolizer.js
@@ -84,14 +84,14 @@ ol.style.Text.prototype.createLiteral = function(featureOrType) {
   var fontFamily = ol.expr.evaluateFeature(this.fontFamily_, feature);
   goog.asserts.assertString(fontFamily, 'fontFamily must be a string');
 
-  var fontSize = ol.expr.evaluateFeature(this.fontSize_, feature);
-  goog.asserts.assertNumber(fontSize, 'fontSize must be a number');
+  var fontSize = Number(ol.expr.evaluateFeature(this.fontSize_, feature));
+  goog.asserts.assert(!isNaN(fontSize), 'fontSize must be a number');
 
   var text = ol.expr.evaluateFeature(this.text_, feature);
   goog.asserts.assertString(text, 'text must be a string');
 
-  var opacity = ol.expr.evaluateFeature(this.opacity_, feature);
-  goog.asserts.assertNumber(opacity, 'opacity must be a number');
+  var opacity = Number(ol.expr.evaluateFeature(this.opacity_, feature));
+  goog.asserts.assert(!isNaN(opacity), 'opacity must be a number');
 
   return new ol.style.TextLiteral({
     color: color,
diff --git a/test/spec/ol/style/fillsymbolizer.test.js b/test/spec/ol/style/fillsymbolizer.test.js
index 14797ced49..b83d2064ca 100644
--- a/test/spec/ol/style/fillsymbolizer.test.js
+++ b/test/spec/ol/style/fillsymbolizer.test.js
@@ -64,6 +64,23 @@ describe('ol.style.Fill', function() {
       expect(literal.fillOpacity).to.be(0.8);
     });
 
+    it('casts opacity to number', function() {
+      var symbolizer = new ol.style.Fill({
+        opacity: ol.expr.parse('opacity'),
+        color: '#ff00ff'
+      });
+
+      var feature = new ol.Feature({
+        opacity: '0.55',
+        geometry: new ol.geom.Polygon(
+            [[[0, 0], [1, 0], [1, 1], [0, 1], [0, 0]]])
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal).to.be.a(ol.style.PolygonLiteral);
+      expect(literal.fillOpacity).to.be(0.55);
+    });
+
   });
 
   describe('#getColor()', function() {
diff --git a/test/spec/ol/style/iconsymbolizer.test.js b/test/spec/ol/style/iconsymbolizer.test.js
index 8433a29435..10cc573af4 100644
--- a/test/spec/ol/style/iconsymbolizer.test.js
+++ b/test/spec/ol/style/iconsymbolizer.test.js
@@ -75,19 +75,82 @@ describe('ol.style.Icon', function() {
       expect(literal.url).to.be('http://example.com/1.png');
     });
 
-    it('applies default type if none provided', function() {
+    it('applies default opacity if none provided', function() {
       var symbolizer = new ol.style.Icon({
-        height: ol.expr.parse('10'),
-        width: ol.expr.parse('20'),
-        url: ol.expr.parse('"http://example.com/1.png"')
+        height: 10,
+        width: 20,
+        url: 'http://example.com/1.png'
       });
 
       var literal = symbolizer.createLiteral(ol.geom.GeometryType.POINT);
       expect(literal).to.be.a(ol.style.IconLiteral);
       expect(literal.opacity).to.be(1);
+    });
+
+    it('applies default rotation if none provided', function() {
+      var symbolizer = new ol.style.Icon({
+        height: 10,
+        width: 20,
+        url: 'http://example.com/1.png'
+      });
+
+      var literal = symbolizer.createLiteral(ol.geom.GeometryType.POINT);
+      expect(literal).to.be.a(ol.style.IconLiteral);
       expect(literal.rotation).to.be(0);
     });
 
+    it('casts opacity to number', function() {
+      var symbolizer = new ol.style.Icon({
+        opacity: ol.expr.parse('opacity'),
+        height: 10,
+        width: 20,
+        url: 'http://example.com/1.png'
+      });
+
+      var feature = new ol.Feature({
+        opacity: '0.53',
+        geometry: new ol.geom.Point([1, 2])
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal).to.be.a(ol.style.IconLiteral);
+      expect(literal.opacity).to.be(0.53);
+    });
+
+    it('casts width to number', function() {
+      var symbolizer = new ol.style.Icon({
+        width: ol.expr.parse('width'),
+        height: 10,
+        url: 'http://example.com/1.png'
+      });
+
+      var feature = new ol.Feature({
+        width: '42',
+        geometry: new ol.geom.Point([1, 2])
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal).to.be.a(ol.style.IconLiteral);
+      expect(literal.width).to.be(42);
+    });
+
+    it('casts height to number', function() {
+      var symbolizer = new ol.style.Icon({
+        height: ol.expr.parse('height'),
+        width: 10,
+        url: 'http://example.com/1.png'
+      });
+
+      var feature = new ol.Feature({
+        height: '42',
+        geometry: new ol.geom.Point([1, 2])
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal).to.be.a(ol.style.IconLiteral);
+      expect(literal.height).to.be(42);
+    });
+
   });
 
   describe('#getHeight()', function() {
diff --git a/test/spec/ol/style/shapesymbolizer.test.js b/test/spec/ol/style/shapesymbolizer.test.js
index 7831c81d00..b20cfb7303 100644
--- a/test/spec/ol/style/shapesymbolizer.test.js
+++ b/test/spec/ol/style/shapesymbolizer.test.js
@@ -71,6 +71,95 @@ describe('ol.style.Shape', function() {
       expect(literal.strokeWidth).to.be(2);
     });
 
+    it('casts size to number', function() {
+      var symbolizer = new ol.style.Shape({
+        size: ol.expr.parse('size'),
+        fill: new ol.style.Fill({
+          color: '#BADA55'
+        }),
+        stroke: new ol.style.Stroke({
+          color: '#013',
+          opacity: 1,
+          width: 2
+        })
+      });
+
+      var feature = new ol.Feature({
+        size: '42',
+        geometry: new ol.geom.Point([1, 2])
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal).to.be.a(ol.style.ShapeLiteral);
+      expect(literal.size).to.be(42);
+    });
+
+    it('casts stroke width to number', function() {
+      var symbolizer = new ol.style.Shape({
+        fill: new ol.style.Fill({
+          color: '#BADA55'
+        }),
+        stroke: new ol.style.Stroke({
+          color: '#013',
+          opacity: 1,
+          width: ol.expr.parse('strokeWidth')
+        })
+      });
+
+      var feature = new ol.Feature({
+        strokeWidth: '4.2',
+        geometry: new ol.geom.Point([1, 2])
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal).to.be.a(ol.style.ShapeLiteral);
+      expect(literal.strokeWidth).to.be(4.2);
+    });
+
+    it('casts stroke opacity to number', function() {
+      var symbolizer = new ol.style.Shape({
+        fill: new ol.style.Fill({
+          color: '#BADA55'
+        }),
+        stroke: new ol.style.Stroke({
+          color: '#013',
+          opacity: ol.expr.parse('strokeOpacity'),
+          width: 3
+        })
+      });
+
+      var feature = new ol.Feature({
+        strokeOpacity: '.2',
+        geometry: new ol.geom.Point([1, 2])
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal).to.be.a(ol.style.ShapeLiteral);
+      expect(literal.strokeOpacity).to.be(0.2);
+    });
+
+    it('casts fill opacity to number', function() {
+      var symbolizer = new ol.style.Shape({
+        fill: new ol.style.Fill({
+          opacity: ol.expr.parse('fillOpacity'),
+          color: '#BADA55'
+        }),
+        stroke: new ol.style.Stroke({
+          color: '#013',
+          width: 3
+        })
+      });
+
+      var feature = new ol.Feature({
+        fillOpacity: '.42',
+        geometry: new ol.geom.Point([1, 2])
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal).to.be.a(ol.style.ShapeLiteral);
+      expect(literal.fillOpacity).to.be(0.42);
+    });
+
   });
 
   describe('#getFill()', function() {
diff --git a/test/spec/ol/style/textsymbolizer.test.js b/test/spec/ol/style/textsymbolizer.test.js
index 85a4113fb9..8319a85782 100644
--- a/test/spec/ol/style/textsymbolizer.test.js
+++ b/test/spec/ol/style/textsymbolizer.test.js
@@ -74,7 +74,7 @@ describe('ol.style.Text', function() {
       expect(literal.opacity).to.be(0.6);
     });
 
-    it('applies default type if none provided', function() {
+    it('applies defaults if none provided', function() {
       var symbolizer = new ol.style.Text({
         text: 'Test'
       });
@@ -88,6 +88,34 @@ describe('ol.style.Text', function() {
       expect(literal.opacity).to.be(1);
     });
 
+    it('casts size to number', function() {
+      var symbolizer = new ol.style.Text({
+        text: 'test',
+        fontSize: ol.expr.parse('size')
+      });
+
+      var feature = new ol.Feature({
+        size: '42'
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal.fontSize).to.be(42);
+    });
+
+    it('casts opacity to number', function() {
+      var symbolizer = new ol.style.Text({
+        text: 'test',
+        opacity: ol.expr.parse('opacity')
+      });
+
+      var feature = new ol.Feature({
+        opacity: '0.42'
+      });
+
+      var literal = symbolizer.createLiteral(feature);
+      expect(literal.opacity).to.be(0.42);
+    });
+
   });
 
   describe('#getColor()', function() {