diff --git a/toolkit/components/telemetry/app/TelemetryEnvironment.sys.mjs b/toolkit/components/telemetry/app/TelemetryEnvironment.sys.mjs
index c68a64346b00..e0d927b0bf27 100644
--- a/toolkit/components/telemetry/app/TelemetryEnvironment.sys.mjs
+++ b/toolkit/components/telemetry/app/TelemetryEnvironment.sys.mjs
@@ -26,8 +26,6 @@ ChromeUtils.defineESModuleGetters(lazy, {
   ProfileAge: "resource://gre/modules/ProfileAge.sys.mjs",
   SearchService: "moz-src:///toolkit/components/search/SearchService.sys.mjs",
   WindowsRegistry: "resource://gre/modules/WindowsRegistry.sys.mjs",
-  WindowsVersionInfo:
-    "resource://gre/modules/components-utils/WindowsVersionInfo.sys.mjs",
 });
 
 ChromeUtils.defineLazyGetter(lazy, "fxAccounts", () => {
@@ -1674,30 +1672,35 @@ EnvironmentCache.prototype = {
       Glean.systemOs.distroVersion.set(this._osData.distroVersion);
     } else if (AppConstants.platform === "win") {
       // The path to the "UBR" key, queried to get additional version details on Windows.
-      const WINDOWS_UBR_KEY_PATH =
+      const CURRENT_VERSION_PATH =
         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
 
-      let versionInfo = lazy.WindowsVersionInfo.get({ throwOnError: false });
-      this._osData.windowsBuildNumber = versionInfo.buildNumber;
-      Glean.systemOs.windowsBuildNumber.set(this._osData.windowsBuildNumber);
-      // We only need the UBR if we're at or above Windows 10.
-      if (
-        typeof this._osData.version === "string" &&
-        Services.vc.compare(this._osData.version, "10") >= 0
-      ) {
-        // Query the UBR key and only add it to the environment if it's available.
-        // |readRegKey| doesn't throw, but rather returns 'undefined' on error.
-        let ubr = lazy.WindowsRegistry.readRegKey(
+      // To make sure the telemetry data is as accurate as possible, use the
+      // build number from the registry. This avoids a future compatibility shim
+      // giving us the wrong value, and we aren't changing behaviour depending
+      // on this so this doesn't circumvent any shim.
+      // See: https://randomascii.wordpress.com/2022/01/06/determinism-bugs-part-two/
+      // Its type is REG_SZ for some reason, so coerce it to a Number.
+      let build = Number(
+        lazy.WindowsRegistry.readRegKey(
           Ci.nsIWindowsRegKey.ROOT_KEY_LOCAL_MACHINE,
-          WINDOWS_UBR_KEY_PATH,
-          "UBR",
+          CURRENT_VERSION_PATH,
+          "CurrentBuild",
           Ci.nsIWindowsRegKey.WOW64_64
-        );
-        if (Number.isInteger(ubr)) {
-          Glean.systemOs.windowsUbr.set(ubr);
-        }
-        this._osData.windowsUBR = ubr !== undefined ? ubr : null;
-      }
+        )
+      );
+      this._osData.windowsBuildNumber = Number.isInteger(build) ? build : null;
+      Glean.systemOs.windowsBuildNumber.set(this._osData.windowsBuildNumber);
+
+      // The UBR value is already a REG_DWORD, so don't coerce it.
+      let ubr = lazy.WindowsRegistry.readRegKey(
+        Ci.nsIWindowsRegKey.ROOT_KEY_LOCAL_MACHINE,
+        CURRENT_VERSION_PATH,
+        "UBR",
+        Ci.nsIWindowsRegKey.WOW64_64
+      );
+      this._osData.windowsUBR = Number.isInteger(ubr) ? ubr : null;
+      Glean.systemOs.windowsUbr.set(ubr);
     }
 
     return this._osData;
diff --git a/toolkit/modules/UpdateUtils.sys.mjs b/toolkit/modules/UpdateUtils.sys.mjs
index 68a60fab0970..53af22577e90 100644
--- a/toolkit/modules/UpdateUtils.sys.mjs
+++ b/toolkit/modules/UpdateUtils.sys.mjs
@@ -8,8 +8,6 @@ const lazy = {};
 
 ChromeUtils.defineESModuleGetters(lazy, {
   WindowsRegistry: "resource://gre/modules/WindowsRegistry.sys.mjs",
-  WindowsVersionInfo:
-    "resource://gre/modules/components-utils/WindowsVersionInfo.sys.mjs",
   ctypes: "resource://gre/modules/ctypes.sys.mjs",
 });
 
@@ -1083,32 +1081,36 @@ ChromeUtils.defineLazyGetter(UpdateUtils, "OSVersion", function () {
 
   if (osVersion) {
     if (AppConstants.platform == "win") {
-      // Add service pack and build number
-      try {
-        const { buildNumber } = lazy.WindowsVersionInfo.get();
-        osVersion += `.0.0.${buildNumber}`;
-      } catch (err) {
-        console.error("Unable to retrieve windows version information: ", err);
+      const CURRENT_VERSION_PATH =
+        "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
+
+      // 'CurrentBuild' is a REG_SZ for some reason, so coerce it to a number
+      // first.
+      let build = Number(
+        lazy.WindowsRegistry.readRegKey(
+          Ci.nsIWindowsRegKey.ROOT_KEY_LOCAL_MACHINE,
+          CURRENT_VERSION_PATH,
+          "CurrentBuild",
+          Ci.nsIWindowsRegKey.WOW64_64
+        )
+      );
+      if (Number.isInteger(build)) {
+        osVersion += `.0.0.${build}`;
+      } else {
         osVersion += ".unknown";
       }
 
-      // add UBR if on Windows 10
-      if (
-        Services.vc.compare(Services.sysinfo.getProperty("version"), "10") >= 0
-      ) {
-        const WINDOWS_UBR_KEY_PATH =
-          "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
-        let ubr = lazy.WindowsRegistry.readRegKey(
-          Ci.nsIWindowsRegKey.ROOT_KEY_LOCAL_MACHINE,
-          WINDOWS_UBR_KEY_PATH,
-          "UBR",
-          Ci.nsIWindowsRegKey.WOW64_64
-        );
-        if (ubr !== undefined) {
-          osVersion += `.${ubr}`;
-        } else {
-          osVersion += ".unknown";
-        }
+      // The value of UBR is already a REG_DWORD, so don't coerce it.
+      let ubr = lazy.WindowsRegistry.readRegKey(
+        Ci.nsIWindowsRegKey.ROOT_KEY_LOCAL_MACHINE,
+        CURRENT_VERSION_PATH,
+        "UBR",
+        Ci.nsIWindowsRegKey.WOW64_64
+      );
+      if (Number.isInteger(ubr)) {
+        osVersion += `.${ubr}`;
+      } else {
+        osVersion += ".unknown";
       }
 
       // Add processor architecture
diff --git a/xpcom/metrics.yaml b/xpcom/metrics.yaml
index e2c0428b138e..f223bc5e2ec8 100644
--- a/xpcom/metrics.yaml
+++ b/xpcom/metrics.yaml
@@ -1435,7 +1435,7 @@ system.os:
     unit: build number
     lifetime: application
     description: |
-      The Windows build number, according to WindowsVersionInfo.
+      The Windows build number, according to 'CurrentBuild' in the Windows registry.
       Windows only.
       e.g. 26100
       Expected in most cases to be identical to `client_info.windows_build_number`.