diff --git a/packages/meteor/asl-helpers-client.js b/packages/meteor/asl-helpers-client.js
index 688ae22205..1026afcb80 100644
--- a/packages/meteor/asl-helpers-client.js
+++ b/packages/meteor/asl-helpers-client.js
@@ -1,3 +1,5 @@
+Meteor.fibersDisabled = true;
+
 Meteor._isPromise = (r) => {
     return r && typeof r.then === 'function';
 };
diff --git a/packages/meteor/asl-helpers.js b/packages/meteor/asl-helpers.js
index f140cc9a3c..1ae0571e7f 100644
--- a/packages/meteor/asl-helpers.js
+++ b/packages/meteor/asl-helpers.js
@@ -2,7 +2,9 @@ const getAslStore = () => (Meteor.isServer && global?.asyncLocalStorage?.getStor
 const getValueFromAslStore = key => getAslStore()[key];
 const updateAslStore = (key, value) => getAslStore()[key] = value;
 
-Meteor._isFibersEnabled = !process.env.DISABLE_FIBERS && Meteor.isServer;
+Meteor.fibersDisabled = !!__meteor_bootstrap__.fibersDisabled;
+Meteor._isFibersEnabled = !Meteor.fibersDisabled;
+
 Meteor._getAslStore = getAslStore;
 Meteor._getValueFromAslStore = getValueFromAslStore;
 Meteor._updateAslStore = updateAslStore;
diff --git a/tools/isobuild/isopack.js b/tools/isobuild/isopack.js
index b1925feaf4..e366afd1b2 100644
--- a/tools/isobuild/isopack.js
+++ b/tools/isobuild/isopack.js
@@ -472,8 +472,19 @@ Object.assign(Isopack.prototype, {
         // case right.)
       }, async function () {
         // Make a new Plugin API object for this plugin.
-        var Plugin = self._makePluginApi(name);
-        await plugin.load({ Plugin: Plugin, Profile: Profile });
+        const Plugin = self._makePluginApi(name);
+        const __meteor_bootstrap__ = {
+          fibersDisabled: true,
+          // Set to null to tell Meteor.startup to call hooks immediately
+          // XXX: should we fully support startup hooks in build plugins?
+          startupHooks: null
+        };
+
+        await plugin.load({
+          Plugin,
+          Profile,
+          __meteor_bootstrap__
+        });
       });
     }
 
diff --git a/tools/static-assets/server/boot.js b/tools/static-assets/server/boot.js
index ca6f586c25..453d30e779 100644
--- a/tools/static-assets/server/boot.js
+++ b/tools/static-assets/server/boot.js
@@ -33,7 +33,8 @@ var starJson = JSON.parse(fs.readFileSync(path.join(buildDir, "star.json")));
 __meteor_bootstrap__ = {
   startupHooks: [],
   serverDir: serverDir,
-  configJson: configJson
+  configJson: configJson,
+  fibersDisabled: true
 };
 
 __meteor_runtime_config__ = {
@@ -504,4 +505,3 @@ var runMain = Profile("Run main()", async function () {
     });
   });
 })().catch(e => console.log('error on boot.js', e));
-
diff --git a/tools/tool-env/isopackets.js b/tools/tool-env/isopackets.js
index d2c21afd6d..acd59e7a40 100644
--- a/tools/tool-env/isopackets.js
+++ b/tools/tool-env/isopackets.js
@@ -303,7 +303,10 @@ var loadIsopacketFromDisk = async function (isopacketName) {
   // An incredibly minimalist version of the environment from
   // tools/server/boot.js.  Kind of a hack.
   var env = {
-    __meteor_bootstrap__: { startupHooks: [] },
+    __meteor_bootstrap__: {
+      startupHooks: [],
+      fibersDisabled: true
+    },
     __meteor_runtime_config__: { meteorRelease: "ISOPACKET" }
   };
   env.Profile = Profile;