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
@@ -595,6 +595,9 @@
           CurPPLexer->LexingRawMode = false;
           IdentifierInfo *IfNDefMacro = nullptr;
           DirectiveEvalResult DER = EvaluateDirectiveExpression(IfNDefMacro);
+          // Stop if Lexer became invalid after hitting code completion token.
+          if (!CurPPLexer)
+            return;
           const bool CondValue = DER.Conditional;
           CurPPLexer->LexingRawMode = true;
           if (Callbacks) {
@@ -3023,6 +3026,10 @@
   IdentifierInfo *IfNDefMacro = nullptr;
   const DirectiveEvalResult DER = EvaluateDirectiveExpression(IfNDefMacro);
   const bool ConditionalTrue = DER.Conditional;
+  // Lexer might become invalid if we hit code completion point while evaluating
+  // 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 +1,6 @@
+#define FOO(X) X
+#if FOO(
+#elif FOO(
+#endif
+// RUN: not %clang_cc1 -fsyntax-only -code-completion-at=%s:2:9 %s
+// RUN: not %clang_cc1 -fsyntax-only -code-completion-at=%s:3:11 %s