2 files changed, 15 insertions, 1 deletions
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index c75cf20eb38..83f2c53a7c6 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -976,7 +976,7 @@ getExplicitVisibilityAux(const NamedDecl *ND,
                            kind);
 
   // Use the most recent declaration.
-  if (!IsMostRecent) {
+  if (!IsMostRecent && !isa<NamespaceDecl>(ND)) {
     const NamedDecl *MostRecent = ND->getMostRecentDecl();
     if (MostRecent != ND)
       return getExplicitVisibilityAux(MostRecent, kind, true);
diff --git a/clang/test/CodeGenCXX/visibility.cpp b/clang/test/CodeGenCXX/visibility.cpp
index 6049bf8d2bc..1c4d5bb8e7a 100644
--- a/clang/test/CodeGenCXX/visibility.cpp
+++ b/clang/test/CodeGenCXX/visibility.cpp
@@ -1295,3 +1295,17 @@ namespace test68 {
   }
   // Check lines at top of file.
 }
+
+namespace test69 {
+  // PR18174
+  namespace foo {
+    void f();
+  }
+  namespace foo {
+    void f() {};
+  }
+  namespace foo __attribute__((visibility("hidden"))) {
+  }
+  // CHECK-LABEL: define void @_ZN6test693foo1fEv
+  // CHECK-HIDDEN-LABEL: define hidden void @_ZN6test693foo1fEv
+}