diff --git a/packages/babel-plugin-transform-block-scoping/src/index.ts b/packages/babel-plugin-transform-block-scoping/src/index.ts
index f50d5fbf1f48..edf7daf82eb9 100644
--- a/packages/babel-plugin-transform-block-scoping/src/index.ts
+++ b/packages/babel-plugin-transform-block-scoping/src/index.ts
@@ -257,16 +257,16 @@ const hoistVarDeclarationsVisitor: Visitor<BlockScoping> = {
   },
 };
 
-interface LoopVisitorState {
+type LoopVisitorState = {
   inSwitchCase: boolean;
   hasBreakContinue: boolean;
   innerLabels: any[];
   hasReturn: boolean;
   ignoreLabeless: boolean;
-  LOOP_IGNORE: symbol;
+  loopIgnored: WeakSet<t.Node>;
   isLoop: boolean;
   map: any;
-}
+};
 
 const loopLabelVisitor: Visitor<LoopVisitorState> = {
   LabeledStatement({ node }, state) {
@@ -332,7 +332,7 @@ const loopVisitor: Visitor<LoopVisitorState> = {
     state,
   ) {
     const { node, scope } = path;
-    if (node[this.LOOP_IGNORE]) return;
+    if (state.loopIgnored.has(node)) return;
 
     let replace;
     let loopText = loopNodeTo(node);
@@ -376,7 +376,7 @@ const loopVisitor: Visitor<LoopVisitorState> = {
 
     if (replace) {
       replace = t.returnStatement(replace);
-      replace[this.LOOP_IGNORE] = true;
+      state.loopIgnored.add(replace);
       path.skip();
       path.replaceWith(t.inherits(replace, node));
     }
@@ -934,7 +934,7 @@ class BlockScoping {
       hasReturn: false,
       isLoop: !!this.loop,
       map: {},
-      LOOP_IGNORE: Symbol(),
+      loopIgnored: new WeakSet(),
     };
 
     this.blockPath.traverse(loopLabelVisitor, state);
diff --git a/packages/babel-plugin-transform-classes/src/index.ts b/packages/babel-plugin-transform-classes/src/index.ts
index e4eb543192f2..598b6a7656bb 100644
--- a/packages/babel-plugin-transform-classes/src/index.ts
+++ b/packages/babel-plugin-transform-classes/src/index.ts
@@ -7,7 +7,7 @@ import globals from "globals";
 import transformClass from "./transformClass";
 import type { Visitor, NodePath } from "@babel/traverse";
 
-const getBuiltinClasses = category =>
+const getBuiltinClasses = (category: string) =>
   Object.keys(globals[category]).filter(name => /^[A-Z]/.test(name));
 
 const builtinClasses = new Set([
@@ -33,7 +33,7 @@ export default declare((api, options: Options) => {
   const noClassCalls = (api.assumption("noClassCalls") ?? loose) as boolean;
 
   // todo: investigate traversal requeueing
-  const VISITED = Symbol();
+  const VISITED = new WeakSet();
 
   return {
     name: "transform-classes",
@@ -58,7 +58,7 @@ export default declare((api, options: Options) => {
 
       ClassExpression(path, state) {
         const { node } = path;
-        if (node[VISITED]) return;
+        if (VISITED.has(node)) return;
 
         const inferred = nameFunction(path);
         if (inferred && inferred !== node) {
@@ -66,7 +66,7 @@ export default declare((api, options: Options) => {
           return;
         }
 
-        node[VISITED] = true;
+        VISITED.add(node);
 
         path.replaceWith(
           transformClass(path, state.file, builtinClasses, loose, {
diff --git a/packages/babel-plugin-transform-modules-systemjs/src/index.ts b/packages/babel-plugin-transform-modules-systemjs/src/index.ts
index c234cf87600a..19ff21f0e890 100644
--- a/packages/babel-plugin-transform-modules-systemjs/src/index.ts
+++ b/packages/babel-plugin-transform-modules-systemjs/src/index.ts
@@ -170,14 +170,14 @@ export default declare<PluginState>((api, options: Options) => {
   api.assertVersion(7);
 
   const { systemGlobal = "System", allowTopLevelThis = false } = options;
-  const IGNORE_REASSIGNMENT_SYMBOL = Symbol();
+  const reassignmentVisited = new WeakSet();
 
   const reassignmentVisitor: Visitor<ReassignmentVisitorState> = {
     "AssignmentExpression|UpdateExpression"(
       path: NodePath<t.AssignmentExpression | t.UpdateExpression>,
     ) {
-      if (path.node[IGNORE_REASSIGNMENT_SYMBOL]) return;
-      path.node[IGNORE_REASSIGNMENT_SYMBOL] = true;
+      if (reassignmentVisited.has(path.node)) return;
+      reassignmentVisited.add(path.node);
 
       const arg = path.isAssignmentExpression()
         ? path.get("left")