diff --git a/tslang/lib/TypeScript/DeclarationPrinter.cpp b/tslang/lib/TypeScript/DeclarationPrinter.cpp
index 3fb0a84a0..e7571125f 100644
--- a/tslang/lib/TypeScript/DeclarationPrinter.cpp
+++ b/tslang/lib/TypeScript/DeclarationPrinter.cpp
@@ -669,6 +669,27 @@ namespace typescript
             newline();
         }
 
+        // index signature ([x: T]: U;) - mirrors the class printer's fix
+        // (see cross-module-class-indexer-shared-gap-fix memory): without
+        // this, a reimporting module's InterfaceInfo::indexes stays empty
+        // and `obj[i]` through the interface fails with "indexer is not
+        // declared" / "Interface member '.index' can't be found".
+        //
+        // Unlike a class's index signature (a plain (arg)->result FunctionType),
+        // an interface's is built via getInterfaceMethodNameAndType with
+        // funcGenContext.thisType set, which prepends an opaque `this` input -
+        // so the real index-argument type is input(1), not input(0) (matching
+        // getIndexSignatureArgumentAndResultTypes's "first parameter is Opaque"
+        // branch in MLIRTypeHelper.h).
+        for (auto indexInfo : interfaceType->indexes)
+        {
+            if (!indexInfo.indexSignature || indexInfo.indexSignature.getNumResults() == 0)
+                continue;
+
+            auto argIndex = indexInfo.indexSignature.getNumInputs() > 1 ? 1 : 0;
+            printIndexer(indexInfo.indexSignature.getInput(argIndex), indexInfo.indexSignature.getResult(0));
+        }
+
         // methods (including static)
         auto opaqueType = mlir_ts::OpaqueType::get(interfaceType->interfaceType.getContext());
         for (auto method : interfaceType->methods)
diff --git a/tslang/test/tester/CMakeLists.txt b/tslang/test/tester/CMakeLists.txt
index ff4a28e74..9ebc986af 100644
--- a/tslang/test/tester/CMakeLists.txt
+++ b/tslang/test/tester/CMakeLists.txt
@@ -886,6 +886,7 @@ add_test(NAME test-compile-export-import-class-static COMMAND test-runner "${PRO
 add_test(NAME test-compile-export-import-class-generic COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_generic.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_generic.ts")
 add_test(NAME test-compile-export-import-class-accessor COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_accessor.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_accessor.ts")
 add_test(NAME test-compile-export-import-class-indexer COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_indexer.ts")
+add_test(NAME test-compile-export-import-interface-indexer COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_interface_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_interface_indexer.ts")
 add_test(NAME test-compile-export-import-class-implements-interface-multilevel COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_implements_interface_multilevel.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_implements_interface_multilevel.ts")
 add_test(NAME test-compile-export-import-class-implements-interface-optional COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_implements_interface_optional.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_implements_interface_optional.ts")
 add_test(NAME test-compile-export-import-class-implements-interface-abstract COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_implements_interface_abstract.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_implements_interface_abstract.ts")
@@ -961,6 +962,7 @@ add_test(NAME test-compile-shared-export-import-class-generic COMMAND test-runne
 # in DeclarationPrinter.cpp.
 add_test(NAME test-compile-shared-export-import-class-accessor COMMAND test-runner -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_accessor.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_accessor.ts")
 add_test(NAME test-compile-shared-export-import-class-indexer COMMAND test-runner -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_indexer.ts")
+add_test(NAME test-compile-shared-export-import-interface-indexer COMMAND test-runner -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_interface_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_interface_indexer.ts")
 add_test(NAME test-compile-shared-export-import-object-literal-with-interface COMMAND test-runner -shared -gctors-as-method "${PROJECT_SOURCE_DIR}/test/tester/tests/import_object_literal_with_interface.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_object_literal_with_interface.ts")
 add_test(NAME test-compile-shared-export-import-object-literal-untyped COMMAND test-runner -shared -gctors-as-method "${PROJECT_SOURCE_DIR}/test/tester/tests/import_object_literal_untyped.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_object_literal_untyped.ts")
 add_test(NAME test-compile-shared-export-import-object-literal-untyped-multi-method COMMAND test-runner -shared -gctors-as-method "${PROJECT_SOURCE_DIR}/test/tester/tests/import_object_literal_untyped_multi_method.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_object_literal_untyped_multi_method.ts")
@@ -1002,6 +1004,7 @@ add_test(NAME test-jit-shared-export-import-class-generic COMMAND test-runner -j
 # FIXED: see the matching test-compile-shared-export-import-class-accessor comment above (2026-07-22).
 add_test(NAME test-jit-shared-export-import-class-accessor COMMAND test-runner -jit -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_accessor.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_accessor.ts")
 add_test(NAME test-jit-shared-export-import-class-indexer COMMAND test-runner -jit -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_indexer.ts")
+add_test(NAME test-jit-shared-export-import-interface-indexer COMMAND test-runner -jit -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_interface_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_interface_indexer.ts")
 add_test(NAME test-jit-shared-export-import-object-literal-with-interface COMMAND test-runner -jit -shared -gctors-as-method "${PROJECT_SOURCE_DIR}/test/tester/tests/import_object_literal_with_interface.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_object_literal_with_interface.ts")
 add_test(NAME test-jit-shared-export-import-object-literal-untyped COMMAND test-runner -jit -shared -gctors-as-method "${PROJECT_SOURCE_DIR}/test/tester/tests/import_object_literal_untyped.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_object_literal_untyped.ts")
 add_test(NAME test-jit-shared-export-import-object-literal-untyped-multi-method COMMAND test-runner -jit -shared -gctors-as-method "${PROJECT_SOURCE_DIR}/test/tester/tests/import_object_literal_untyped_multi_method.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_object_literal_untyped_multi_method.ts")
diff --git a/tslang/test/tester/tests/export_interface_indexer.ts b/tslang/test/tester/tests/export_interface_indexer.ts
new file mode 100644
index 000000000..8b9b6eb6e
--- /dev/null
+++ b/tslang/test/tester/tests/export_interface_indexer.ts
@@ -0,0 +1,13 @@
+namespace M {
+
+    // Cross-module counterpart to 00interface_indexer.ts - an exported
+    // interface with an index signature, cast-to from an importer-side class
+    // implementation. See cross-module-class-indexer-shared-gap-fix memory:
+    // DeclarationPrinter never re-emits a class's index signature for
+    // -shared reimport; interfaces may share the same gap since their
+    // print() function also never mentions `indexes`/InterfaceIndexInfo.
+
+    export interface Storage {
+        [index: number]: string;
+    }
+}
diff --git a/tslang/test/tester/tests/import_interface_indexer.ts b/tslang/test/tester/tests/import_interface_indexer.ts
new file mode 100644
index 000000000..8ec16c8aa
--- /dev/null
+++ b/tslang/test/tester/tests/import_interface_indexer.ts
@@ -0,0 +1,25 @@
+import './export_interface_indexer'
+
+class Impl {
+    #val: string = "";
+
+    [index: number]: string;
+
+    get(index: number): string {
+        return this.#val;
+    }
+
+    set(index: number, value: string) {
+        this.#val = value;
+    }
+}
+
+function main() {
+    const impl = new Impl();
+    const s: M.Storage = impl;
+
+    s[0] = "hi";
+    assert(s[0] == "hi");
+
+    print("done.");
+}