Index: lib/Lex/Preprocessor.cpp
===================================================================
--- lib/Lex/Preprocessor.cpp
+++ lib/Lex/Preprocessor.cpp
@@ -773,8 +773,13 @@
     }
   } while (!ReturnedToken);
 
-  if (Result.is(tok::code_completion))
+  if (Result.is(tok::code_completion) && Result.getIdentifierInfo()) {
+    // Remember the identifier before code completion token.
     setCodeCompletionIdentifierInfo(Result.getIdentifierInfo());
+    // Set IdenfitierInfo to null to avoid confusing code that handles both
+    // identifiers and completion tokens.
+    Result.setIdentifierInfo(nullptr);
+  }
 
   LastTokenWasAt = Result.is(tok::at);
 }
Index: test/CodeCompletion/inside-macros.cpp
===================================================================
--- /dev/null
+++ test/CodeCompletion/inside-macros.cpp
@@ -0,0 +1,13 @@
+#define ID(X) X
+
+void test(bool input_var) {
+  ID(input_var) = true;
+  // Check that input_var shows up when completing at the start, in the middle
+  // and at the end of the identifier.
+  //
+  // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:4:6 %s -o - | FileCheck %s
+  // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:4:8 %s -o - | FileCheck %s
+  // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:4:15 %s -o - | FileCheck %s
+
+  // CHECK: input_var
+}