diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index e38d6546ea7..8e0d2c2e78e 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -32101,7 +32101,7 @@ namespace ts {
             amalgamatedDuplicates = createMap();
 
             // Initialize global symbol table
-            let augmentations: (StringLiteral | Identifier)[][] | undefined;
+            let augmentations: (readonly (StringLiteral | Identifier)[])[] | undefined;
             for (const file of host.getSourceFiles()) {
                 if (file.redirectInfo) {
                     continue;
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 6b90430fb86..6f545d71d18 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2773,7 +2773,7 @@ namespace ts {
         /* @internal */ resolvedTypeReferenceDirectiveNames: Map<ResolvedTypeReferenceDirective | undefined>;
         /* @internal */ imports: readonly StringLiteralLike[];
         // Identifier only if `declare global`
-        /* @internal */ moduleAugmentations: (StringLiteral | Identifier)[];
+        /* @internal */ moduleAugmentations: readonly (StringLiteral | Identifier)[];
         /* @internal */ patternAmbientModules?: PatternAmbientModule[];
         /* @internal */ ambientModuleNames: readonly string[];
         /* @internal */ checkJsDirective?: CheckJsDirective;