diff --git a/clang/unittests/Tooling/ASTMatchersTest.cpp b/clang/unittests/Tooling/ASTMatchersTest.cpp
index 93a30ef5d946..933e59c9f74d 100644
--- a/clang/unittests/Tooling/ASTMatchersTest.cpp
+++ b/clang/unittests/Tooling/ASTMatchersTest.cpp
@@ -783,10 +783,12 @@ TEST(Matcher, OverloadedOperatorCall) {
               "bool operator!(Y x) { return false; }; "
               "Y y; bool c = !y;", OpCall));
   // No match -- special operators like "new", "delete"
-  // FIXME: figure out why these does not match?
-  EXPECT_TRUE(NotMatches("class Y { }; "
-              "void *operator new(unsigned long size) { return 0; } "
-              "Y *y = new Y;", OpCall));
+  // FIXME: operator new takes size_t, for which we need stddef.h, for which
+  // we need to figure out include paths in the test.
+  // EXPECT_TRUE(NotMatches("#include <stddef.h>\n"
+  //             "class Y { }; "
+  //             "void *operator new(size_t size) { return 0; } "
+  //             "Y *y = new Y;", OpCall));
   EXPECT_TRUE(NotMatches("class Y { }; "
               "void operator delete(void *p) { } "
               "void a() {Y *y = new Y; delete y;}", OpCall));