diff --git a/src/sheet.ts b/src/sheet.ts
index fdeb0e868..b5ca31419 100644
--- a/src/sheet.ts
+++ b/src/sheet.ts
@@ -142,20 +142,14 @@ export class StyleSheet extends MutationObserver {
                             }
                         }
                     }
-                } else {
-                    if (target.isConnected) {
-                        classNames.forEach((className) => {
-                            if (!oldClassNames.includes(className)) {
-                                addClassName(className);
-                            }
-                        })
-                        for (const oldClassName of oldClassNames) {
-                            if (!classNames.contains(oldClassName)) {
-                                removeClassName(oldClassName);
-                            }
+                } else if (target.isConnected) {
+                    classNames.forEach((className) => {
+                        if (!oldClassNames.includes(className)) {
+                            addClassName(className);
                         }
-                    } else {
-                        for (const oldClassName of oldClassNames) {
+                    })
+                    for (const oldClassName of oldClassNames) {
+                        if (!classNames.contains(oldClassName)) {
                             removeClassName(oldClassName);
                         }
                     }