diff --git a/cc/afdo.go b/cc/afdo.go
index 23d196d..5c587c0 100644
--- a/cc/afdo.go
+++ b/cc/afdo.go
@@ -84,6 +84,7 @@
 		// 3. Make the profile searchable by the build system. So it's used the next time the binary
 		//	  is built.
 		flags.Local.CFlags = append([]string{"-funique-internal-linkage-names"}, flags.Local.CFlags...)
+		flags.Local.CFlags = append([]string{"-mllvm", "-enable-fs-discriminator=true"}, flags.Local.CFlags...)
 	}
 	if path := afdo.Properties.FdoProfilePath; path != nil {
 		// The flags are prepended to allow overriding.