diff --git a/src/codeql.ts b/src/codeql.ts
index 422f41c80..594b58eb2 100644
--- a/src/codeql.ts
+++ b/src/codeql.ts
@@ -226,6 +226,15 @@ export interface CodeQL {
 export interface VersionInfo {
   version: string;
   features?: { [name: string]: boolean };
+  /**
+   * The overlay version helps deal with backward incompatible changes for
+   * overlay analysis. When a precompiled query pack reports the same overlay
+   * version as the CodeQL CLI, we can use the CodeQL CLI to perform overlay
+   * analysis with that pack. Otherwise, if the overlay versions are different,
+   * or if either the pack or the CLI does not report an overlay version,
+   * we need to revert to non-overlay analysis.
+   */
+  overlayVersion?: number;
 }
 
 export interface ResolveLanguagesOutput {
diff --git a/src/testing-utils.ts b/src/testing-utils.ts
index 11df50dc6..d7d486bd5 100644
--- a/src/testing-utils.ts
+++ b/src/testing-utils.ts
@@ -254,18 +254,21 @@ export function mockLanguagesInRepo(languages: string[]) {
 export const makeVersionInfo = (
   version: string,
   features?: { [name: string]: boolean },
+  overlayVersion?: number,
 ): codeql.VersionInfo => ({
   version,
   features,
+  overlayVersion,
 });
 
 export function mockCodeQLVersion(
   version: string,
   features?: { [name: string]: boolean },
+  overlayVersion?: number,
 ) {
   return codeql.createStubCodeQL({
     async getVersion() {
-      return makeVersionInfo(version, features);
+      return makeVersionInfo(version, features, overlayVersion);
     },
   });
 }