diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h
@@ -325,13 +325,19 @@
   /// \param[in] name
   ///     The name to be considered.
   ///
+  /// \param[in] namespace_decl
+  ///     The namespace decl that this name is being searched. This can be
+  ///     invalid if we are searching the root namespace.
+  ///
   /// \param[in] ignore_all_dollar_names
   ///     True if $-names of all sorts should be ignored.
   ///
   /// \return
   ///     True if the name is one of a class of names that are ignored by
   ///     global lookup for performance reasons.
-  bool IgnoreName(const ConstString name, bool ignore_all_dollar_names);
+  bool IgnoreName(const ConstString name,
+                  const CompilerDeclContext &namespace_decl,
+                  bool ignore_all_dollar_names);
 
 public:
   /// Copies a single Decl into the parser's AST context.
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
@@ -574,13 +574,23 @@
 }
 
 bool ClangASTSource::IgnoreName(const ConstString name,
+                                const CompilerDeclContext &namespace_decl,
                                 bool ignore_all_dollar_names) {
-  static const ConstString id_name("id");
-  static const ConstString Class_name("Class");
-
-  if (m_ast_context->getLangOpts().ObjC)
-    if (name == id_name || name == Class_name)
+  if (m_ast_context->getLangOpts().ObjC) {
+    static const ConstString id_name("id");
+    static const ConstString Class_name("Class");
+    if (name == id_name || name == Class_name) {
+      // Only disallow using "id" and "Class" if we are searching from the root
+      // namespace or translation unit level. If namespace_decl is valid, then
+      // this is not the root namespace.
+      if (namespace_decl.IsValid())
+        return false;
+      LLDB_LOG(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS),
+               "  CAS::IgnoreName(name=\"{0}\") Ignoring reserved keryword",
+               name);
       return true;
+    }
+  }
 
   StringRef name_string_ref = name.GetStringRef();
 
@@ -600,7 +610,7 @@
   SymbolContextList sc_list;
 
   const ConstString name(context.m_decl_name.getAsString().c_str());
-  if (IgnoreName(name, true))
+  if (IgnoreName(name, namespace_decl, true))
     return;
 
   if (!m_target)
@@ -663,7 +673,7 @@
     NameSearchContext &context, lldb::ModuleSP module_sp,
     const CompilerDeclContext &namespace_decl) {
   const ConstString name(context.m_decl_name.getAsString().c_str());
-  if (IgnoreName(name, true))
+  if (IgnoreName(name, namespace_decl, true))
     return;
 
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
@@ -1321,7 +1321,7 @@
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
   const ConstString name(context.m_decl_name.getAsString().c_str());
-  if (IgnoreName(name, false))
+  if (IgnoreName(name, namespace_decl, false))
     return;
 
   // Only look for functions by name out in our symbols if the function doesn't
diff --git a/lldb/test/API/commands/expression/ignore/Makefile b/lldb/test/API/commands/expression/ignore/Makefile
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/commands/expression/ignore/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/commands/expression/ignore/TestIgnoreName.py b/lldb/test/API/commands/expression/ignore/TestIgnoreName.py
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/commands/expression/ignore/TestIgnoreName.py
@@ -0,0 +1,39 @@
+"""
+Test calling user defined functions using expression evaluation.
+This test checks that typesystem lookup works correctly for typedefs of
+untagged structures.
+
+Ticket: https://llvm.org/bugs/show_bug.cgi?id=26790
+"""
+
+
+import lldb
+
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestIgnoreName(TestBase):
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test(self):
+        """Test that we can evaluate an expression that finds something inside
+           a namespace that uses an Objective C keyword.
+        """
+        self.build()
+        exe_path = self.getBuildArtifact("a.out")
+        error = lldb.SBError()
+        triple = None
+        platform = None
+        add_dependent_modules = False
+        target = self.dbg.CreateTarget(exe_path, triple, platform,
+                                       add_dependent_modules, error)
+        self.assertTrue(error.Success(), "Make sure our target got created")
+        expr_result = target.EvaluateExpression("a::Class a; a")
+        self.assertTrue(expr_result.GetError().Success(),
+                        "Make sure our expression evaluated without errors")
+        self.assertTrue(expr_result.GetValue() == None,
+                        'Expression value is None')
+        self.assertTrue(expr_result.GetType().GetName() == "a::Class",
+                        'Expression result type is "a::Class"')
diff --git a/lldb/test/API/commands/expression/ignore/main.cpp b/lldb/test/API/commands/expression/ignore/main.cpp
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/commands/expression/ignore/main.cpp
@@ -0,0 +1,10 @@
+namespace a {
+  struct Class {
+  };
+}
+
+int main(int argc, char **argv)
+{
+  a::Class c;
+  return 0;
+}