Index: lldb/source/Core/IOHandler.cpp
===================================================================
--- lldb/source/Core/IOHandler.cpp
+++ lldb/source/Core/IOHandler.cpp
@@ -233,7 +233,7 @@
         matches, descriptions);
   case Completion::Expression: {
     CompletionResult result;
-    CompletionRequest request(current_line, current_line - cursor,
+    CompletionRequest request(current_line, cursor - current_line,
                               skip_first_n_matches, max_matches, result);
     CommandCompletions::InvokeCommonCompletionCallbacks(
         io_handler.GetDebugger().GetCommandInterpreter(),