diff --git a/pkgs/os-specific/bsd/netbsd/pkgs/netbsdSetupHook/setup-hook.sh b/pkgs/os-specific/bsd/netbsd/pkgs/netbsdSetupHook/setup-hook.sh
index 8c3742a76534..d05461ad10cb 100644
--- a/pkgs/os-specific/bsd/netbsd/pkgs/netbsdSetupHook/setup-hook.sh
+++ b/pkgs/os-specific/bsd/netbsd/pkgs/netbsdSetupHook/setup-hook.sh
@@ -1,6 +1,6 @@
 addNetBSDMakeFlags() {
-  makeFlags="INCSDIR=${!outputDev}/include $makeFlags"
-  makeFlags="MANDIR=${!outputMan}/share/man $makeFlags"
+  prependToVar makeFlags "INCSDIR=${!outputDev}/include"
+  prependToVar makeFlags "MANDIR=${!outputMan}/share/man"
 }
 
 preConfigureHooks+=(addNetBSDMakeFlags)