diff --git a/modules/system/boot/systemd.nix b/modules/system/boot/systemd.nix
index aa0b679ea2f5..2413509790d3 100644
--- a/modules/system/boot/systemd.nix
+++ b/modules/system/boot/systemd.nix
@@ -229,7 +229,8 @@ let
 
           [Service]
           Environment=PATH=${def.path}
-          ${concatMapStrings (n: "Environment=${n}=${getAttr n def.environment}\n") (attrNames def.environment)}
+          ${let env = cfg.globalEnvironment // def.environment;
+            in concatMapStrings (n: "Environment=${n}=${getAttr n env}\n") (attrNames env)}
           ${optionalString (!def.restartIfChanged) "X-RestartIfChanged=false"}
 
           ${optionalString (def.preStart != "") ''
@@ -391,6 +392,15 @@ in
       description = "Default unit started when the system boots.";
     };
 
+    boot.systemd.globalEnvironment = mkOption {
+      type = types.attrs;
+      default = {};
+      example = { TZ = "CET"; };
+      description = ''
+        Environment variables passed to <emphasis>all</emphasis> systemd units.
+      '';
+    };
+
     services.journald.console = mkOption {
       default = "";
       type = types.uniq types.string;
diff --git a/modules/system/upstart/upstart.nix b/modules/system/upstart/upstart.nix
index cfde1cc07538..44e6e8bb63b5 100644
--- a/modules/system/upstart/upstart.nix
+++ b/modules/system/upstart/upstart.nix
@@ -19,7 +19,7 @@ let
     let
       hasMain = job.script != "" || job.exec != "";
 
-      env = config.system.upstartEnvironment // job.environment;
+      env = job.environment;
 
       preStartScript = makeJobScript "${job.name}-pre-start"
         ''
@@ -270,15 +270,6 @@ in
       options = [ jobOptions upstartJob ];
     };
 
-    system.upstartEnvironment = mkOption {
-      type = types.attrs;
-      default = {};
-      example = { TZ = "CET"; };
-      description = ''
-        Environment variables passed to <emphasis>all</emphasis> Upstart jobs.
-      '';
-    };
-
   };
 
 
diff --git a/modules/testing/test-instrumentation.nix b/modules/testing/test-instrumentation.nix
index c6c95e63af1b..8ceffbcb9ec6 100644
--- a/modules/testing/test-instrumentation.nix
+++ b/modules/testing/test-instrumentation.nix
@@ -55,10 +55,6 @@ let kernel = config.boot.kernelPackages.kernel; in
 
         # Coverage data is written into /tmp/coverage-data.
         mkdir -p /tmp/xchg/coverage-data
-
-        # Mount debugfs to gain access to the kernel coverage data (if
-        # available).
-        mount -t debugfs none /sys/kernel/debug || true
       '';
 
     # If the kernel has been built with coverage instrumentation, make
@@ -80,7 +76,7 @@ let kernel = config.boot.kernelPackages.kernel; in
     networking.defaultGateway = mkOverride 150 "";
     networking.nameservers = mkOverride 150 [ ];
 
-    system.upstartEnvironment.GCOV_PREFIX = "/tmp/xchg/coverage-data";
+    boot.systemd.globalEnvironment.GCOV_PREFIX = "/tmp/xchg/coverage-data";
 
     system.requiredKernelConfig = with config.lib.kernelConfig; [
       (isYes "SERIAL_8250_CONSOLE")