diff --git a/frontend/src/app/main/ui/workspace/sidebar/branch_review/common.cljs b/frontend/src/app/main/ui/workspace/sidebar/branch_review/common.cljs
index cf978891c0..e3c0b021cf 100644
--- a/frontend/src/app/main/ui/workspace/sidebar/branch_review/common.cljs
+++ b/frontend/src/app/main/ui/workspace/sidebar/branch_review/common.cljs
@@ -190,11 +190,15 @@
 (defn- fmt-number
   "At most two decimals, trailing zeros stripped (89.99999 -> \"90\",
   439.4999 -> \"439.5\", 386 -> \"386\"), grouped and punctuated the way
-  the active locale writes numbers (\"439,5\" in Spanish)."
+  the active locale writes numbers (\"439,5\" in Spanish). It goes
+  through `Intl.NumberFormat`: once a plugin has loaded, the SES lockdown
+  turns `Number.prototype.toLocaleString` into `toString`, options and
+  all."
   [v]
-  (let [locale (-> i18n/*current-locale*
-                   (str/replace "_" "-"))]
-    (.toLocaleString v locale #js {:maximumFractionDigits 2})))
+  (let [locale (or (some-> i18n/*current-locale*
+                           (str/replace "_" "-"))
+                   js/undefined)]
+    (.format (js/Intl.NumberFormat. locale #js {:maximumFractionDigits 2}) v)))
 
 (defn- short-str
   [v]
diff --git a/frontend/test/frontend_tests/ui/branches_compare_labels_test.cljs b/frontend/test/frontend_tests/ui/branches_compare_labels_test.cljs
index f5363d4c72..4fe8f2058c 100644
--- a/frontend/test/frontend_tests/ui/branches_compare_labels_test.cljs
+++ b/frontend/test/frontend_tests/ui/branches_compare_labels_test.cljs
@@ -69,3 +69,17 @@
     (t/is (= "439.5" (display-val 439.5)))
     (t/is (= "90" (display-val 89.99999)) "at most two decimals")
     (t/is (= "386" (display-val 386)))))
+
+(t/deftest numbers-keep-two-decimals-under-the-plugin-lockdown
+  ;; a loaded plugin's SES lockdown turns `toLocaleString` into
+  ;; `toString`, which ignores the options
+  (let [proto    (.-prototype js/Number)
+        original (.-toLocaleString proto)]
+    (set! (.-toLocaleString proto) (.-toString proto))
+    (try
+      (binding [i18n/*current-locale* "en"]
+        (t/is (= "163" (display-val 162.99999952316284))))
+      (binding [i18n/*current-locale* nil]
+        (t/is (= "1.5" (display-val 1.5)) "no locale falls back to the default"))
+      (finally
+        (set! (.-toLocaleString proto) original)))))