Index: lib/AST/DeclBase.cpp
===================================================================
--- lib/AST/DeclBase.cpp
+++ lib/AST/DeclBase.cpp
@@ -1700,8 +1700,15 @@
 
 DeclContext *DeclContext::getRedeclContext() {
   DeclContext *Ctx = this;
-  // Skip through transparent contexts.
-  while (Ctx->isTransparentContext())
+
+  // In C, the redeclaration context for enumerators is the translation unit,
+  // so we skip through transparent contexts as well as struct/union contexts.
+  bool SkipRecords = getDeclKind() == Decl::Kind::Enum &&
+                     !getParentASTContext().getLangOpts().CPlusPlus;
+
+  // Skip through contexts to get to the redeclaration context. Transparent
+  // contexts are always skipped.
+  while ((SkipRecords && Ctx->isRecord()) || Ctx->isTransparentContext())
     Ctx = Ctx->getParent();
   return Ctx;
 }
Index: test/Sema/enum.c
===================================================================
--- test/Sema/enum.c
+++ test/Sema/enum.c
@@ -135,3 +135,26 @@
   };
   int makeStructNonEmpty;
 };
+
+static int EnumRedecl; // expected-note 2 {{previous definition is here}}
+struct S {
+  enum {
+    EnumRedecl = 4 // expected-error {{redefinition of 'EnumRedecl'}}
+  } e;
+};
+
+union U {
+  enum {
+    EnumRedecl = 5 // expected-error {{redefinition of 'EnumRedecl'}}
+  } e;
+};
+
+enum PR15071 {
+  PR15071_One // expected-note {{previous definition is here}}
+};
+
+struct EnumRedeclStruct {
+  enum {
+    PR15071_One // expected-error {{redefinition of enumerator 'PR15071_One'}}
+  } e;
+};