diff --git a/packages/mermaid/src/diagrams/treemap/parser.ts b/packages/mermaid/src/diagrams/treemap/parser.ts
index 4d71ff470..9bf4c5b10 100644
--- a/packages/mermaid/src/diagrams/treemap/parser.ts
+++ b/packages/mermaid/src/diagrams/treemap/parser.ts
@@ -21,7 +21,7 @@ const populate = (ast: TreemapAst, db: TreemapDB) => {
     type: string;
     value?: number;
     classSelector?: string;
-    cssCompiledStyles?: string;
+    cssCompiledStyles?: string[];
   }[] = [];
 
   // Extract classes and styles from the treemap
@@ -44,7 +44,7 @@ const populate = (ast: TreemapAst, db: TreemapDB) => {
 
     // Get styles as a string if they exist
     const styles = item.classSelector ? db.getStylesForClass(item.classSelector) : [];
-    const cssCompiledStyles = styles.length > 0 ? styles.join(';') : undefined;
+    const cssCompiledStyles = styles.length > 0 ? styles : undefined;
 
     const itemData = {
       level,
diff --git a/packages/mermaid/src/diagrams/treemap/utils.ts b/packages/mermaid/src/diagrams/treemap/utils.ts
index e7e7fcc5c..07c7b0140 100644
--- a/packages/mermaid/src/diagrams/treemap/utils.ts
+++ b/packages/mermaid/src/diagrams/treemap/utils.ts
@@ -12,7 +12,7 @@ export function buildHierarchy(
     type: string;
     value?: number;
     classSelector?: string;
-    cssCompiledStyles?: string;
+    cssCompiledStyles?: string[];
   }[]
 ): TreemapNode[] {
   if (!items.length) {
@@ -29,7 +29,7 @@ export function buildHierarchy(
     };
     node.classSelector = item?.classSelector;
     if (item?.cssCompiledStyles) {
-      node.cssCompiledStyles = [item.cssCompiledStyles];
+      node.cssCompiledStyles = item.cssCompiledStyles;
     }
 
     if (item.type === 'Leaf' && item.value !== undefined) {