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
@@ -1537,7 +1537,11 @@
       if (Map) {
         StoredDeclsMap::iterator Pos = Map->find(ND->getDeclName());
         assert(Pos != Map->end() && "no lookup entry for decl");
-        Pos->second.remove(ND);
+        StoredDeclsList &List = Pos->second;
+        List.remove(ND);
+        // Clean up the entry if there are no more decls.
+        if (List.isNull())
+          Map->erase(Pos);
       }
     } while (DC->isTransparentContext() && (DC = DC->getParent()));
   }
diff --git a/clang/unittests/AST/ASTImporterTest.cpp b/clang/unittests/AST/ASTImporterTest.cpp
--- a/clang/unittests/AST/ASTImporterTest.cpp
+++ b/clang/unittests/AST/ASTImporterTest.cpp
@@ -4279,6 +4279,10 @@
   // This asserts in the old implementation.
   DC->removeDecl(A0);
   EXPECT_FALSE(DC->containsDecl(A0));
+
+  // Make sure we do not leave a StoredDeclsList with no entries.
+  DC->removeDecl(A1);
+  ASSERT_EQ(Map->find(A1->getDeclName()), Map->end());
 }
 
 struct ImportFunctionTemplateSpecializations