diff --git a/packages/babel-plugin-transform-block-scoping/src/annex-B_3_3.ts b/packages/babel-plugin-transform-block-scoping/src/annex-B_3_3.ts
index 79ac2cb0200b..346c1bdcbc74 100644
--- a/packages/babel-plugin-transform-block-scoping/src/annex-B_3_3.ts
+++ b/packages/babel-plugin-transform-block-scoping/src/annex-B_3_3.ts
@@ -51,6 +51,8 @@ export const annexB33FunctionsVisitor: Visitor = {
 function transformStatementList(paths: NodePath<t.Statement>[]) {
   outer: for (const path of paths) {
     if (!path.isFunctionDeclaration()) continue;
+    // Annex B.3.3 only applies to plain functions.
+    if (path.node.async || path.node.generator) return;
 
     const { scope } = path.parentPath;
     if (isVarScope(scope)) return;
@@ -74,9 +76,6 @@ function maybeTransformBlockScopedFunction(
     parentPath: { scope },
   } = path;
 
-  // Annex B.3.3 only applies to plain functions.
-  if (node.async || node.generator) return;
-
   const { id } = node;
   scope.removeOwnBinding(id.name);
   node.id = null;
@@ -115,7 +114,11 @@ function isStrict(path: NodePath) {
   return !!path.find(({ node }) => {
     if (t.isProgram(node)) {
       if (node.sourceType === "module") return true;
-    } else if (!t.isBlockStatement(node)) return false;
+    } else if (t.isClass(node)) {
+      return true;
+    } else if (!t.isBlockStatement(node)) {
+      return false;
+    }
 
     return node.directives?.some(
       directive => directive.value.value === "use strict",
diff --git a/packages/babel-plugin-transform-block-scoping/src/index.ts b/packages/babel-plugin-transform-block-scoping/src/index.ts
index 9f664f3efc2f..9b578fcf5409 100644
--- a/packages/babel-plugin-transform-block-scoping/src/index.ts
+++ b/packages/babel-plugin-transform-block-scoping/src/index.ts
@@ -93,7 +93,7 @@ export default declare((api, opts: Options) => {
 
             if (headPath?.isVariableDeclaration<t.Node>()) {
               // If we wrap the loop body, we transform the var
-              // declaration in the loop head now, to avoid having
+              // declaration in the loop head now, to avoid
               // invalid references that break other plugins:
               //
               //  for (let head of x) {
diff --git a/packages/babel-plugin-transform-block-scoping/src/loop.ts b/packages/babel-plugin-transform-block-scoping/src/loop.ts
index 3a1b27084781..05c5908e631d 100644
--- a/packages/babel-plugin-transform-block-scoping/src/loop.ts
+++ b/packages/babel-plugin-transform-block-scoping/src/loop.ts
@@ -75,7 +75,7 @@ function relativeLoopLocation(path: NodePath, loopPath: NodePath<t.Loop>) {
   let inClosure = false;
 
   for (let currPath = path; currPath; currPath = currPath.parentPath) {
-    if (currPath.isFunction()) inClosure = true;
+    if (currPath.isFunction() || currPath.isClass()) inClosure = true;
     if (currPath === bodyPath) {
       return { inBody: true, inClosure };
     } else if (currPath === loopPath) {
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async-generator/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async-generator/input.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async-generator/input.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async-generator/input.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async-generator/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async-generator/output.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async-generator/output.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async-generator/output.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async/input.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/input.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async/input.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/options.json b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async/options.json
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/options.json
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async/options.json
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async/output.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/output.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-async/output.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-const/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-const/input.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-const/input.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-const/input.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-const/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-const/output.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-const/output.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-const/output.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-let/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-let/input.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-let/input.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-let/input.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-let/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-let/output.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-let/output.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-let/output.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-var/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-var/input.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-var/input.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-var/input.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-var/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-var/output.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-collision-var/output.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-collision-var/output.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-generator/input.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/input.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-generator/input.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/options.json b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-generator/options.json
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/options.json
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-generator/options.json
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-generator/output.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/output.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-generator/output.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/exec.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/exec.js
new file mode 100644
index 000000000000..b7308d71d5a0
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/exec.js
@@ -0,0 +1,17 @@
+class A {
+  m() {
+    if (true) {
+      function f() {
+        return true;
+      }
+    }
+
+    function g() {
+      return f();
+    }
+
+    return g();
+  }
+}
+
+expect(new A().m).toThrow(ReferenceError);
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/input.js
new file mode 100644
index 000000000000..b7308d71d5a0
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/input.js
@@ -0,0 +1,17 @@
+class A {
+  m() {
+    if (true) {
+      function f() {
+        return true;
+      }
+    }
+
+    function g() {
+      return f();
+    }
+
+    return g();
+  }
+}
+
+expect(new A().m).toThrow(ReferenceError);
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/output.js
new file mode 100644
index 000000000000..5e870864f2b0
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-class/output.js
@@ -0,0 +1,14 @@
+class A {
+  m() {
+    if (true) {
+      var _f = function () {
+        return true;
+      };
+    }
+    function g() {
+      return f();
+    }
+    return g();
+  }
+}
+expect(new A().m).toThrow(ReferenceError);
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/input.js
new file mode 100644
index 000000000000..04519fd7a1ee
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/input.js
@@ -0,0 +1,11 @@
+const m = module {
+  if (true) {
+    function f() {
+      return true;
+    }
+  }
+
+  function g() {
+    return f();
+  }
+};
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/options.json b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/options.json
new file mode 100644
index 000000000000..19328f031d2e
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/options.json
@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    "transform-block-scoping",
+    "transform-block-scoped-functions",
+    "syntax-module-blocks"
+  ]
+}
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/output.js
new file mode 100644
index 000000000000..b583fee7d2fc
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-in-module-expression/output.js
@@ -0,0 +1,10 @@
+var m = module {
+  if (true) {
+    var _f = function () {
+      return true;
+    };
+  }
+  function g() {
+    return f();
+  }
+};
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-module/input.mjs b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-module/input.mjs
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-module/input.mjs
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-module/input.mjs
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-module/output.mjs b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-module/output.mjs
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-module/output.mjs
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3-module/output.mjs
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3/input.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046/input.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3/input.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3/output.js
similarity index 100%
rename from packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046/output.js
rename to packages/babel-plugin-transform-block-scoping/test/fixtures/general/annex-B_3_3/output.js
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-strict/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-strict/input.js
deleted file mode 100644
index 26283df2072e..000000000000
--- a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-strict/input.js
+++ /dev/null
@@ -1,11 +0,0 @@
-"use strict";
-
-if (true) {
-  function run() {
-    return true;
-  }
-}
-
-function test() {
-  return run();
-}
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-strict/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-strict/output.js
deleted file mode 100644
index 6ad0f6e042a7..000000000000
--- a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-strict/output.js
+++ /dev/null
@@ -1,10 +0,0 @@
-"use strict";
-
-if (true) {
-  var _run = function () {
-    return true;
-  };
-}
-function test() {
-  return run();
-}
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/exec.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/exec.js
new file mode 100644
index 000000000000..fb0aa668e016
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/exec.js
@@ -0,0 +1,10 @@
+let run = [];
+
+for (let i = 0; i < 2; i++) {
+  run.push(class C {
+    x = i;
+  });
+}
+
+expect(new run[0]().x).toBe(0);
+expect(new run[1]().x).toBe(1);
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/input.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/input.js
new file mode 100644
index 000000000000..f6a35700916a
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/input.js
@@ -0,0 +1,5 @@
+for (let i = 0; i < 2; i++) {
+  class C {
+    x = i;
+  }
+}
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/output.js
new file mode 100644
index 000000000000..54716df47a75
--- /dev/null
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/loop-closure-in-class/output.js
@@ -0,0 +1,8 @@
+var _loop = function (i) {
+  class C {
+    x = i;
+  }
+};
+for (var i = 0; i < 2; i++) {
+  _loop(i);
+}