diff --git a/compileopts/config.go b/compileopts/config.go
index 39fc4f2a..fb5d4575 100644
--- a/compileopts/config.go
+++ b/compileopts/config.go
@@ -269,6 +269,7 @@ func (c *Config) CFlags() []string {
 		root := goenv.Get("TINYGOROOT")
 		cflags = append(cflags,
 			"--sysroot="+filepath.Join(root, "lib/macos-minimal-sdk/src"),
+			"-isystem", filepath.Join(root, "lib/macos-minimal-sdk/src/usr/include"), // necessary for Nix
 		)
 	case "picolibc":
 		root := goenv.Get("TINYGOROOT")