diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -1212,7 +1212,8 @@
     return getPrimaryContext()->Encloses(DC);
 
   for (; DC; DC = DC->getParent())
-    if (!isa<LinkageSpecDecl>(DC) && DC->getPrimaryContext() == this)
+    if (!isa<LinkageSpecDecl>(DC) && !isa<ExportDecl>(DC) &&
+        DC->getPrimaryContext() == this)
       return true;
   return false;
 }
diff --git a/clang/test/SemaCXX/lookup-through-export.cpp b/clang/test/SemaCXX/lookup-through-export.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/lookup-through-export.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -std=c++20 %s -verify
+
+// expected-no-diagnostics
+export module X;
+export {
+  namespace A {
+  namespace B {
+  int bar;
+  }
+  } // namespace A
+  namespace C {
+  void foo() {
+    using namespace A;
+    (void)B::bar;
+  }
+  } // namespace C
+}
+
+export {
+  namespace D {
+  namespace E {
+  int bar;
+  }
+  } // namespace D
+  namespace F {
+  void foo() {
+    using namespace D;
+    (void)E::bar;
+  }
+  } // namespace F
+}