diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -2266,10 +2266,15 @@
 
         SourceLocation LParenLoc = PP.getLocForEndOfToken(OpTok.getLocation());
         SourceLocation RParenLoc = PP.getLocForEndOfToken(PrevTokLocation);
-        Diag(LParenLoc, diag::err_expected_parentheses_around_typename)
-          << OpTok.getName()
-          << FixItHint::CreateInsertion(LParenLoc, "(")
-          << FixItHint::CreateInsertion(RParenLoc, ")");
+        if (LParenLoc.isInvalid() || RParenLoc.isInvalid()) {
+          Diag(OpTok.getLocation(),
+               diag::err_expected_parentheses_around_typename)
+              << OpTok.getName();
+        } else {
+          Diag(LParenLoc, diag::err_expected_parentheses_around_typename)
+              << OpTok.getName() << FixItHint::CreateInsertion(LParenLoc, "(")
+              << FixItHint::CreateInsertion(RParenLoc, ")");
+        }
         isCastExpr = true;
         return ExprEmpty();
       }
diff --git a/clang/test/Parser/sizeof-missing-parens.c b/clang/test/Parser/sizeof-missing-parens.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Parser/sizeof-missing-parens.c
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void Foo(int);
+
+#define Bar(x) Foo(x)
+
+void Baz() {
+  Foo(sizeof int); // expected-error {{expected parentheses around type name in sizeof expression}}
+  Bar(sizeof int); // expected-error {{expected parentheses around type name in sizeof expression}}
+}