diff --git a/unittests/IR/IRBuilderTest.cpp b/unittests/IR/IRBuilderTest.cpp
index 1812cd39d13..5b27fd66360 100644
--- a/unittests/IR/IRBuilderTest.cpp
+++ b/unittests/IR/IRBuilderTest.cpp
@@ -245,6 +245,7 @@ TEST_F(IRBuilderTest, FastMathFlags) {
   EXPECT_FALSE(FDiv->getFastMathFlags().any());
   FDiv->setHasAllowReciprocal(true);
   FAdd->setHasAllowReciprocal(false);
+  FAdd->setHasNoNaNs(true);
   FDiv->copyFastMathFlags(FAdd);
   EXPECT_TRUE(FDiv->hasNoNaNs());
   EXPECT_FALSE(FDiv->hasAllowReciprocal());