Index: source/Commands/CommandObjectExpression.cpp
===================================================================
--- source/Commands/CommandObjectExpression.cpp
+++ source/Commands/CommandObjectExpression.cpp
@@ -296,6 +296,20 @@
         options.SetTryAllThreads(m_command_options.try_all_threads);
         options.SetDebug(m_command_options.debug);
         
+        // If the language is unknown, set it to the langage of the
+        // frame's CU.
+        if (options.GetLanguage() == lldb::eLanguageTypeUnknown &&
+            exe_ctx.HasFrameScope())
+        {
+            StackFrame *frame = exe_ctx.GetFramePtr();
+            if (frame)
+            {
+                CompileUnit *cu = frame->GetSymbolContext(eSymbolContextCompUnit).comp_unit;
+                if (cu)
+                    options.SetLanguage(cu->GetLanguage());
+            }
+        }
+
         // If there is any chance we are going to stop and want to see
         // what went wrong with our expression, we should generate debug info
         if (!m_command_options.ignore_breakpoints ||
Index: source/Expression/ClangExpressionParser.cpp
===================================================================
--- source/Expression/ClangExpressionParser.cpp
+++ source/Expression/ClangExpressionParser.cpp
@@ -214,6 +214,9 @@
     case lldb::eLanguageTypeObjC:
         m_compiler->getLangOpts().ObjC1 = true;
         m_compiler->getLangOpts().ObjC2 = true;
+        // ObjC++ syntax is allowed when debugging ObjC code, so we
+        // set it here as well.
+        m_compiler->getLangOpts().CPlusPlus = true;
         break;
     case lldb::eLanguageTypeC_plus_plus:
         m_compiler->getLangOpts().CPlusPlus = true;