diff --git a/release.nix b/release.nix
index d4db1d36..560295fb 100644
--- a/release.nix
+++ b/release.nix
@@ -42,18 +42,12 @@ rec {
     let
 
       aws-sdk-cpp' =
-        lib.overrideDerivation (aws-sdk-cpp.override {
+        aws-sdk-cpp.override {
           apis = ["s3"];
           customMemoryManagement = false;
-        }) (attrs: {
-          src = fetchFromGitHub {
-            owner = "edolstra";
-            repo = "aws-sdk-cpp";
-            rev = "d1e2479f79c24e2a1df8a3f3ef3278a1c6383b1e";
-            sha256 = "1vhgsxkhpai9a7dk38q4r239l6dsz2jvl8hii24c194lsga3g84h";
-          };
-        });
+        };
 
+        /*
       nix = overrideDerivation nixUnstable (attrs: {
         src = fetchFromGitHub {
           owner = "NixOS";
@@ -66,6 +60,8 @@ rec {
         configureFlags = attrs.configureFlags + " --disable-doc-gen";
         preConfigure = "./bootstrap.sh; mkdir -p $doc $man";
       });
+      */
+      nix = nixUnstable;
 
       perlDeps = buildEnv {
         name = "hydra-perl-deps";
diff --git a/src/hydra-queue-runner/build-remote.cc b/src/hydra-queue-runner/build-remote.cc
index 05a4bab0..f1c86e1d 100644
--- a/src/hydra-queue-runner/build-remote.cc
+++ b/src/hydra-queue-runner/build-remote.cc
@@ -184,7 +184,7 @@ void State::buildRemote(ref<Store> destStore,
                 throw Error("machine ‘%1%’ does not support repeating a build; please upgrade it to Nix 1.12", machine->sshName);
 
         } catch (EndOfFile & e) {
-            child.pid.wait(true);
+            child.pid.wait();
             string s = chomp(readFile(result.logFile));
             throw Error(format("cannot connect to ‘%1%’: %2%") % machine->sshName % s);
         }
@@ -428,7 +428,7 @@ void State::buildRemote(ref<Store> destStore,
 
         /* Shut down the connection. */
         child.to = -1;
-        child.pid.wait(true);
+        child.pid.wait();
 
     } catch (Error & e) {
         /* Disable this machine until a certain period of time has
diff --git a/src/hydra-queue-runner/hydra-queue-runner.cc b/src/hydra-queue-runner/hydra-queue-runner.cc
index a531714a..99b8707a 100644
--- a/src/hydra-queue-runner/hydra-queue-runner.cc
+++ b/src/hydra-queue-runner/hydra-queue-runner.cc
@@ -459,7 +459,7 @@ void State::logCompressor()
                 throw SysError("cannot start bzip2");
             });
 
-            int res = pid.wait(true);
+            int res = pid.wait();
 
             if (res != 0)
                 throw Error(format("bzip2 returned exit code %1% while compressing ‘%2%’")
@@ -521,7 +521,7 @@ void State::notificationSender()
                 throw SysError("cannot start hydra-notify");
             });
 
-            int res = pid.wait(true);
+            int res = pid.wait();
 
             if (res != 0)
                 throw Error(format("hydra-build returned exit code %1% notifying about build %2%")