diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -3023,6 +3023,10 @@
   IdentifierInfo *IfNDefMacro = nullptr;
   const DirectiveEvalResult DER = EvaluateDirectiveExpression(IfNDefMacro);
   const bool ConditionalTrue = DER.Conditional;
+  // Lexer might become invalid if we hit code completion point while evulating
+  // expression.
+  if (!CurPPLexer)
+    return;
 
   // If this condition is equivalent to #ifndef X, and if this is the first
   // directive seen, handle it for the multiple-include optimization.
diff --git a/clang/test/CodeCompletion/crash-if-directive.cpp b/clang/test/CodeCompletion/crash-if-directive.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeCompletion/crash-if-directive.cpp
@@ -0,0 +1,3 @@
+#define FOO(X) X + 1
+#if FOO(
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:2:9 %s | FileCheck %s --allow-empty