diff --git a/pkgs/development/tools/misc/hydra/default.nix b/pkgs/development/tools/misc/hydra/default.nix
index a4f1a96c6a4..e3d2c4950bc 100644
--- a/pkgs/development/tools/misc/hydra/default.nix
+++ b/pkgs/development/tools/misc/hydra/default.nix
@@ -118,7 +118,7 @@ in releaseTools.nixBuild rec {
 
   preCheck = ''
     patchShebangs .
-    export LOGNAME=${LOGNAME:-foo}
+    export LOGNAME=''${LOGNAME:-foo}
   '';
 
   postInstall = ''
diff --git a/pkgs/servers/amqp/rabbitmq-server/default.nix b/pkgs/servers/amqp/rabbitmq-server/default.nix
index 5bf3f2e693e..7725a7272ed 100644
--- a/pkgs/servers/amqp/rabbitmq-server/default.nix
+++ b/pkgs/servers/amqp/rabbitmq-server/default.nix
@@ -36,7 +36,7 @@ stdenv.mkDerivation rec {
 
   postInstall =
     ''
-      echo 'PATH=${erlang}/bin:${PATH:+:}$PATH' >> $out/sbin/rabbitmq-env
+      echo 'PATH=${erlang}/bin:''${PATH:+:}$PATH' >> $out/sbin/rabbitmq-env
     ''; # */
 
   meta = {