diff --git a/packages/babel-helper-create-class-features-plugin/src/index.ts b/packages/babel-helper-create-class-features-plugin/src/index.ts
index 6698e246570a..1cf906740986 100644
--- a/packages/babel-helper-create-class-features-plugin/src/index.ts
+++ b/packages/babel-helper-create-class-features-plugin/src/index.ts
@@ -96,9 +96,20 @@ export function createClassFeaturePlugin({
     pre(file) {
       enableFeature(file, feature, loose);
 
+      let existingVersion = file.get(versionKey);
+      if (!process.env.BABEL_8_BREAKING) {
+        if (typeof existingVersion === "number") {
+          // Up to version 7.21.4, we used to encode the version as a number
+          // using the following encoding algorithm:
+          //   version.split(".").reduce((v, x) => v * 1e5 + +x, 0)
+          const patch = existingVersion % 1e5;
+          const minor = ((existingVersion - patch) / 1e5) % 1e5;
+          existingVersion = `7.${minor}.${patch}`;
+        }
+      }
       if (
-        !file.get(versionKey) ||
-        semver.lt(file.get(versionKey), PACKAGE_JSON.version)
+        !existingVersion ||
+        semver.lt(existingVersion, PACKAGE_JSON.version)
       ) {
         file.set(versionKey, PACKAGE_JSON.version);
       }
diff --git a/packages/babel-helper-create-regexp-features-plugin/src/index.ts b/packages/babel-helper-create-regexp-features-plugin/src/index.ts
index 95c5cdda8c52..24cc1000ef21 100644
--- a/packages/babel-helper-create-regexp-features-plugin/src/index.ts
+++ b/packages/babel-helper-create-regexp-features-plugin/src/index.ts
@@ -82,9 +82,20 @@ export function createRegExpFeaturePlugin({
         }
       }
 
+      let existingVersion = file.get(versionKey);
+      if (!process.env.BABEL_8_BREAKING) {
+        if (typeof existingVersion === "number") {
+          // Up to version 7.21.4, we used to encode the version as a number
+          // using the following encoding algorithm:
+          //   version.split(".").reduce((v, x) => v * 1e5 + +x, 0)
+          const patch = existingVersion % 1e5;
+          const minor = ((existingVersion - patch) / 1e5) % 1e5;
+          existingVersion = `7.${minor}.${patch}`;
+        }
+      }
       if (
-        !file.has(versionKey) ||
-        semver.lt(file.get(versionKey), PACKAGE_JSON.version)
+        !existingVersion ||
+        semver.lt(existingVersion, PACKAGE_JSON.version)
       ) {
         file.set(versionKey, PACKAGE_JSON.version);
       }