diff --git a/pkgs/development/libraries/gettext/gettext-setup-hook.sh b/pkgs/development/libraries/gettext/gettext-setup-hook.sh
index ad3763c29b64..69020146f84d 100644
--- a/pkgs/development/libraries/gettext/gettext-setup-hook.sh
+++ b/pkgs/development/libraries/gettext/gettext-setup-hook.sh
@@ -10,7 +10,7 @@ addEnvHooks "$hostOffset" gettextDataDirsHook
 
 # libintl must be listed in load flags on non-Glibc
 # it doesn't hurt to have it in Glibc either though
-if [ -n "@gettextNeedsLdflags@" -a -z "$dontAddExtraLibs" ]; then
+if [ -n "@gettextNeedsLdflags@" -a -z "${dontAddExtraLibs-}" ]; then
     # See pkgs/build-support/setup-hooks/role.bash
     getHostRole
     export NIX_${role_pre}LDFLAGS+=" -lintl"
diff --git a/pkgs/development/libraries/libiconv/setup-hook.sh b/pkgs/development/libraries/libiconv/setup-hook.sh
index f89361a62998..120cf06c61b5 100644
--- a/pkgs/development/libraries/libiconv/setup-hook.sh
+++ b/pkgs/development/libraries/libiconv/setup-hook.sh
@@ -2,7 +2,7 @@
 # it doesn't hurt to have it in Glibc either though
 
 # See pkgs/build-support/setup-hooks/role.bash
-if [ -z "$dontAddExtraLibs" ]; then
+if [ -z "${dontAddExtraLibs-}" ]; then
     getHostRole
     export NIX_${role_pre}LDFLAGS+=" -liconv"
 fi