diff --git a/kas/corstone1000-firmware-only.yml b/kas/corstone1000-firmware-only.yml
index 6192a4087234..bc47940b316b 100644
--- a/kas/corstone1000-firmware-only.yml
+++ b/kas/corstone1000-firmware-only.yml
@@ -10,7 +10,7 @@ local_conf_header:
     OVERRIDES .= ":firmware"
 
     # Need to ensure we build with a small libc
-    TCLIBC="musl"
+    TCLIBC = "musl"
 
   mass-storage: |
     # Ensure the Mass Storage device is absent
diff --git a/meta-arm/conf/multiconfig/firmware.conf b/meta-arm/conf/multiconfig/firmware.conf
index 95de4d246792..018c0deb81e5 100644
--- a/meta-arm/conf/multiconfig/firmware.conf
+++ b/meta-arm/conf/multiconfig/firmware.conf
@@ -4,7 +4,7 @@
 DISTROOVERRIDES = "firmware"
 
 TMPDIR:append = "_${MACHINE}"
-TCLIBC="musl"
+TCLIBC = "musl"
 
 # Ignore the testimage flags to include ssh-server-dropbear
 IMAGE_CLASSES:remove = "testimage"