diff --git a/package-lock.json b/package-lock.json
index 84e3f85..2bf1acd 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -30,7 +30,7 @@
         "eslint-plugin-react": "^7.24.0",
         "eslint-plugin-react-hooks": "^4.2.0",
         "extensionless": "^1.9.9",
-        "geostyler-style": "9.2.0",
+        "geostyler-style": "^9.2.0",
         "jsdom": "^24.1.0",
         "ol": "^9.1.0",
         "rimraf": "^3.0.2",
diff --git a/package.json b/package.json
index 71e005e..251c497 100644
--- a/package.json
+++ b/package.json
@@ -56,7 +56,7 @@
     "eslint-plugin-react": "^7.24.0",
     "eslint-plugin-react-hooks": "^4.2.0",
     "extensionless": "^1.9.9",
-    "geostyler-style": "9.2.0",
+    "geostyler-style": "^9.2.0",
     "jsdom": "^24.1.0",
     "ol": "^9.1.0",
     "rimraf": "^3.0.2",
diff --git a/src/LegendRenderer/LegendRenderer.ts b/src/LegendRenderer/LegendRenderer.ts
index 1863f9d..071a8e1 100644
--- a/src/LegendRenderer/LegendRenderer.ts
+++ b/src/LegendRenderer/LegendRenderer.ts
@@ -5,6 +5,10 @@ import OlGeomPolygon from 'ol/geom/Polygon';
 import OlGeomLineString from 'ol/geom/LineString';
 import OlStyle from 'ol/style/Style';
 import Renderer from 'ol/render/canvas/Immediate';
+import {
+  isRule,
+  isSymbolizer
+} from 'geostyler-style';
 import { create as createTransform } from 'ol/transform';
 import {
   Style,
@@ -126,6 +130,10 @@ export class LegendRenderer {
    * @param {Symbolizer} symbolizer the symbolizer object
    */
   getGeometryForSymbolizer(symbolizer: Symbolizer): OlGeometry {
+    if (!isSymbolizer(symbolizer)) {
+      throw new Error('Invalid symbolizer');
+    }
+
     const kind = symbolizer.kind;
     switch (kind) {
       case 'Mark':
@@ -154,6 +162,10 @@ export class LegendRenderer {
    * @param {Object} rule the geostyler rule
    */
   getRuleIcon(rule: Rule): Promise<string> {
+    if (!isRule(rule)) {
+      return Promise.reject('Invalid rule');
+    }
+
     const canvas = document.createElement('canvas');
     canvas.setAttribute('width', `${iconSize[0]}`);
     canvas.setAttribute('height', `${iconSize[1]}`);
@@ -163,6 +175,7 @@ export class LegendRenderer {
     const transform = createTransform();
     const renderer = new Renderer(context as CanvasRenderingContext2D, pixelRatio, extent, transform, 0);
     const geoms: OlGeometry[] = [];
+
     rule.symbolizers.forEach(symbolizer => geoms.push(this.getGeometryForSymbolizer(symbolizer)));
 
     const styleParser = new OlStyleParser();