diff --git a/src/core/finalize.ts b/src/core/finalize.ts
index 82f4a728..d83c040a 100644
--- a/src/core/finalize.ts
+++ b/src/core/finalize.ts
@@ -133,7 +133,7 @@ function finalizeProperty(
 		} else return
 	}
 	// Search new objects for unfinalized drafts. Frozen objects should never contain drafts.
-	if (isDraftable(childValue) && !Object.isFrozen(childValue)) {
+	if (isDraftable(childValue) && !isFrozen(childValue)) {
 		if (!rootScope.immer_.autoFreeze_ && rootScope.unfinalizedDrafts_ < 1) {
 			// optimization: if an object is not a draft, and we don't have to
 			// deepfreeze everything, and we are sure that no drafts are left in the remaining object
diff --git a/src/utils/common.ts b/src/utils/common.ts
index c1259970..ab3d2623 100644
--- a/src/utils/common.ts
+++ b/src/utils/common.ts
@@ -180,7 +180,7 @@ export function shallowCopy(base: any) {
 }
 
 export function freeze(obj: any, deep: boolean): void {
-	if (Object.isFrozen(obj) || isDraft(obj) || !isDraftable(obj)) return
+	if (isFrozen(obj) || isDraft(obj) || !isDraftable(obj)) return
 	if (getArchtype(obj) > 1 /* Map or Set */) {
 		obj.set = obj.add = obj.clear = obj.delete = dontMutateFrozenCollections as any
 	}