diff --git a/meta/recipes-devtools/expect/expect_5.45.4.bb b/meta/recipes-devtools/expect/expect_5.45.4.bb
index a89b48ef1c..f1d30d8217 100644
--- a/meta/recipes-devtools/expect/expect_5.45.4.bb
+++ b/meta/recipes-devtools/expect/expect_5.45.4.bb
@@ -41,7 +41,7 @@ S = "${WORKDIR}/${BPN}${PV}"
 
 EXTRA_AUTORECONF += "--exclude=aclocal"
 
-CFLAGS += "-std=gnu17"
+CFLAGS:append = " -std=gnu17"
 
 do_install:append() {
     mv ${D}${libdir}/expect${PV}/libexpect*.so ${D}${libdir}/