Index: lib/AST/ExternalASTMerger.cpp
===================================================================
--- lib/AST/ExternalASTMerger.cpp
+++ lib/AST/ExternalASTMerger.cpp
@@ -41,6 +41,7 @@
   Decl *Imported(Decl *From, Decl *To) override {
     if (auto ToTag = dyn_cast<TagDecl>(To)) {
       ToTag->setHasExternalLexicalStorage();
+      ToTag->setMustBuildLookupTable();
     } else if (auto ToNamespace = dyn_cast<NamespaceDecl>(To)) {
       ToNamespace->setHasExternalVisibleStorage();
     }
Index: test/Import/indirect-struct-member-access/Inputs/S.c
===================================================================
--- /dev/null
+++ test/Import/indirect-struct-member-access/Inputs/S.c
@@ -0,0 +1,3 @@
+struct S {
+  int a;
+};
Index: test/Import/indirect-struct-member-access/test.c
===================================================================
--- /dev/null
+++ test/Import/indirect-struct-member-access/test.c
@@ -0,0 +1,4 @@
+// RUN: clang-import-test -import %S/Inputs/S.c -expression %s
+void expr(struct S *MyS) {
+  MyS->a = 3;
+}