diff --git a/core/block_svg.ts b/core/block_svg.ts
index acead527a..0da81f01d 100644
--- a/core/block_svg.ts
+++ b/core/block_svg.ts
@@ -1178,7 +1178,10 @@ export class BlockSvg
       .getRenderer()
       .getConstants()
       .getBlockStyle(blockStyleName);
-    this.styleName_ = blockStyleName;
+
+    if (this.styleName_) {
+      dom.removeClass(this.svgGroup_, this.styleName_);
+    }
 
     if (blockStyle) {
       this.hat = blockStyle.hat;
@@ -1188,6 +1191,9 @@ export class BlockSvg
       this.style = blockStyle;
 
       this.applyColour();
+
+      dom.addClass(this.svgGroup_, blockStyleName);
+      this.styleName_ = blockStyleName;
     } else {
       throw Error('Invalid style name: ' + blockStyleName);
     }