diff --git a/src/Core/Style.js b/src/Core/Style.js
index 6a09ffe300..bd57ad4c19 100644
--- a/src/Core/Style.js
+++ b/src/Core/Style.js
@@ -212,14 +212,14 @@ function defineStyleCategory(style, category, userValue) {
                     return value;
                 }
                 style[category] = {};
-                value = userValue;
-                if (userValue instanceof Function) { // always true
+                value = { ...userValue };
+                if (userValue instanceof Function) {
                     value = readExpression(userValue, style.context);
                 }
                 defaultRules[category].keys.forEach((key) => {
-                    defineStyleProperty(style, category, key, value[key], defaultRules[category].defaultValue[key]);
+                    defineStyleProperty(style, category, key, value[key], defaultRules[category].defaultValue?.[key]);// zoom has no defaultValue
                 });
-                defaultRules[category].ifKeys.forEach((key) => {
+                defaultRules[category].ifKeys?.forEach((key) => { // zoom, stroke, text and icon have no ifKeys
                     if (value[key] != undefined) {
                         defineStyleProperty(style, category, key, value[key]);
                     }
@@ -545,93 +545,17 @@ class Style {
         params.text = params.text || {};
         params.icon = params.icon || {};
 
-        if (params.zoom instanceof Function) {
-            defineStyleCategory(this, 'zoom', params.zoom);
-        } else {
-            this.zoom = {};
-            defineStyleProperty(this, 'zoom', 'min', params.zoom.min);
-            defineStyleProperty(this, 'zoom', 'max', params.zoom.max);
-        }
-
-        if (params.fill instanceof Function) {
-            defineStyleCategory(this, 'fill', params.fill);
-        } else {
-            this.fill = {};
-            defineStyleProperty(this, 'fill', 'color', params.fill.color);
-            defineStyleProperty(this, 'fill', 'opacity', params.fill.opacity, 1.0);
-            defineStyleProperty(this, 'fill', 'pattern', params.fill.pattern);
-            defineStyleProperty(this, 'fill', 'base_altitude', params.fill.base_altitude, baseAltitudeDefault);
-            if (params.fill.extrusion_height) {
-                defineStyleProperty(this, 'fill', 'extrusion_height', params.fill.extrusion_height);
-            }
-        }
-
-        if (params.stroke instanceof Function) {
-            defineStyleCategory(this, 'stroke', params.stroke);
-        } else {
-            this.stroke = {};
-            defineStyleProperty(this, 'stroke', 'color', params.stroke.color);
-            defineStyleProperty(this, 'stroke', 'opacity', params.stroke.opacity, 1.0);
-            defineStyleProperty(this, 'stroke', 'width', params.stroke.width, 1.0);
-            defineStyleProperty(this, 'stroke', 'dasharray', params.stroke.dasharray, []);
-            defineStyleProperty(this, 'stroke', 'base_altitude', params.stroke.base_altitude, baseAltitudeDefault);
-        }
-
-        if (params.point instanceof Function) {
-            defineStyleCategory(this, 'point', params.point);
-        } else {
-            this.point = {};
-            defineStyleProperty(this, 'point', 'color', params.point.color);
-            defineStyleProperty(this, 'point', 'line', params.point.line);
-            defineStyleProperty(this, 'point', 'opacity', params.point.opacity, 1.0);
-            defineStyleProperty(this, 'point', 'radius', params.point.radius, 2.0);
-            defineStyleProperty(this, 'point', 'width', params.point.width, 0.0);
-            defineStyleProperty(this, 'point', 'base_altitude', params.point.base_altitude, baseAltitudeDefault);
-            if (params.point.model) {
-                defineStyleProperty(this, 'point', 'model', params.point.model);
-            }
+        if (params.icon.key) {
+            console.warn("'icon.key' is deprecated: use 'icon.id' instead");
+            params.icon.id = params.icon.key;
         }
 
-        if (params.text instanceof Function) {
-            defineStyleCategory(this, 'text', params.text);
-        } else {
-            this.text = {};
-            defineStyleProperty(this, 'text', 'field', params.text.field);
-            defineStyleProperty(this, 'text', 'zOrder', params.text.zOrder, 'auto');
-            defineStyleProperty(this, 'text', 'color', params.text.color, '#000000');
-            defineStyleProperty(this, 'text', 'anchor', params.text.anchor, 'center');
-            defineStyleProperty(this, 'text', 'offset', params.text.offset, [0, 0]);
-            defineStyleProperty(this, 'text', 'padding', params.text.padding, 2);
-            defineStyleProperty(this, 'text', 'size', params.text.size, 16);
-            defineStyleProperty(this, 'text', 'placement', params.text.placement, 'point');
-            defineStyleProperty(this, 'text', 'rotation', params.text.rotation, 'auto');
-            defineStyleProperty(this, 'text', 'wrap', params.text.wrap, 10);
-            defineStyleProperty(this, 'text', 'spacing', params.text.spacing, 0);
-            defineStyleProperty(this, 'text', 'transform', params.text.transform, 'none');
-            defineStyleProperty(this, 'text', 'justify', params.text.justify, 'center');
-            defineStyleProperty(this, 'text', 'opacity', params.text.opacity, 1.0);
-            defineStyleProperty(this, 'text', 'font', params.text.font, ['Open Sans Regular', 'Arial Unicode MS Regular', 'sans-serif']);
-            defineStyleProperty(this, 'text', 'haloColor', params.text.haloColor, '#000000');
-            defineStyleProperty(this, 'text', 'haloWidth', params.text.haloWidth, 0);
-            defineStyleProperty(this, 'text', 'haloBlur', params.text.haloBlur, 0);
-        }
-
-        if (params.icon instanceof Function) {
-            defineStyleCategory(this, 'icon', params.icon);
-        } else {
-            this.icon = {};
-            defineStyleProperty(this, 'icon', 'source', params.icon.source);
-            if (params.icon.key) {
-                console.warn("'icon.key' is deprecated: use 'icon.id' instead");
-                params.icon.id = params.icon.key;
-            }
-            defineStyleProperty(this, 'icon', 'id', params.icon.id);
-            defineStyleProperty(this, 'icon', 'cropValues', params.icon.cropValues);
-            defineStyleProperty(this, 'icon', 'anchor', params.icon.anchor, 'center');
-            defineStyleProperty(this, 'icon', 'size', params.icon.size, 1);
-            defineStyleProperty(this, 'icon', 'color', params.icon.color);
-            defineStyleProperty(this, 'icon', 'opacity', params.icon.opacity, 1.0);
-        }
+        defineStyleCategory(this, 'zoom', params.zoom);
+        defineStyleCategory(this, 'fill', params.fill);
+        defineStyleCategory(this, 'stroke', params.stroke);
+        defineStyleCategory(this, 'point', params.point);
+        defineStyleCategory(this, 'text', params.text);
+        defineStyleCategory(this, 'icon', params.icon);
     }
 
     setContext(ctx) {
diff --git a/test/unit/style.js b/test/unit/style.js
index 75239efa86..3f58a801e2 100644
--- a/test/unit/style.js
+++ b/test/unit/style.js
@@ -32,35 +32,34 @@ describe('Style', function () {
         stubFetcherTexture.restore();
     });
 
-    const styleOpt = {
-        fill: {
-            color: 'blue',
-            opacity: {
-                stops: [[10, '{opacity}']], // Mapbox vectorTile
-            },
-            pattern: {
-                // Mock MapBox StyleExpression() instance
-                expression: { evaluate: () => 'pattern' },
+    it('Instanciate style from styleOpt and context', function _it() {
+        const styleOpt = {
+            fill: {
+                color: 'blue',
+                opacity: {
+                    stops: [[10, '{opacity}']], // Mapbox vectorTile
+                },
+                pattern: {
+                    // Mock MapBox StyleExpression() instance
+                    expression: { evaluate: () => 'pattern' },
+                },
+                extrusion_height: {
+                    stops: [[10, (p, ctx) => 10 + ctx.coordinates.z]],
+                },
             },
-            extrusion_height: {
-                stops: [[10, (p, ctx) => 10 + ctx.coordinates.z]],
+        };
+        const ctx = {
+            coordinates: { z: -2 },
+            properties: {
+                opacity: -3,
             },
-        },
-    };
-    const ctx = {
-        coordinates: { z: -2 },
-        properties: {
-            opacity: -3,
-        },
-    };
-
-    const style = new Style(styleOpt);
-    style.point.color = 'red';
-    style.setContext(ctx);
-    // mock StyleContext() instance
-    style.context.featureStyle = { stroke: { color: 'pink' } };
+        };
+        const style = new Style(styleOpt);
+        style.point.color = 'red';
+        style.setContext(ctx);
+        // mock StyleContext() instance
+        style.context.featureStyle = { stroke: { color: 'pink' } };
 
-    it('Instanciate style from styleOpt and context', function _it() {
         // no default value
         assert.equal(style.point.line, undefined);
         // defaultValue is value
@@ -82,6 +81,44 @@ describe('Style', function () {
         assert.equal(style.stroke.color, 'pink');
     });
 
+    it('Instanciate style from fct at category level', function _it() {
+        const fill = () => ({
+            color: 'blue',
+            opacity: {
+                stops: [[10, '{opacity}']], // Mapbox vectorTile
+            },
+            pattern: {
+                // Mock MapBox StyleExpression() instance
+                expression: { evaluate: () => 'pattern' },
+            },
+            extrusion_height: {
+                stops: [[10, (p, ctx) => 10 + ctx.coordinates.z]],
+            },
+        });
+        const styleOpt = {
+            fill,
+        };
+        const ctx = {
+            coordinates: { z: -2 },
+            properties: {
+                opacity: -3,
+            },
+        };
+        const style = new Style(styleOpt);
+        style.setContext(ctx);
+        // mock StyleContext() instance
+        style.context.featureStyle = { stroke: { color: 'pink' } };
+
+        // userValue
+        assert.equal(style.fill.color, fill().color);
+        // userValue with stops & {}
+        assert.equal(style.fill.opacity, ctx.properties.opacity);
+        // userValue as MapBox expression
+        assert.equal(style.fill.pattern, fill().pattern.expression.evaluate());
+        // userValue with stops & function
+        assert.equal(style.fill.extrusion_height, fill().extrusion_height.stops[0][1](2, ctx));
+    });
+
     describe('applyToCanvasPolygon()', () => {
         const styleOpt = {
             point: {},