diff --git a/frontend/src/ts/popups/custom-test-duration-popup.ts b/frontend/src/ts/popups/custom-test-duration-popup.ts
index ccf0e15b1..6d485b87f 100644
--- a/frontend/src/ts/popups/custom-test-duration-popup.ts
+++ b/frontend/src/ts/popups/custom-test-duration-popup.ts
@@ -101,7 +101,7 @@ export function hide(): void {
 function apply(): void {
   const val = parseInput($("#customTestDurationPopup input").val() as string);
 
-  if (val !== null && !isNaN(val) && val >= 0) {
+  if (val !== null && !isNaN(val) && val >= 0 && isFinite(val)) {
     UpdateConfig.setTimeConfig(val as MonkeyTypes.TimeModes);
     ManualRestart.set();
     TestLogic.restart();
diff --git a/frontend/src/ts/popups/custom-word-amount-popup.ts b/frontend/src/ts/popups/custom-word-amount-popup.ts
index 4b2c440ca..433899884 100644
--- a/frontend/src/ts/popups/custom-word-amount-popup.ts
+++ b/frontend/src/ts/popups/custom-word-amount-popup.ts
@@ -35,7 +35,7 @@ export function hide(): void {
 function apply(): void {
   const val = parseInt($("#customWordAmountPopup input").val() as string);
 
-  if (val !== null && !isNaN(val) && val >= 0) {
+  if (val !== null && !isNaN(val) && val >= 0 && isFinite(val)) {
     UpdateConfig.setWordCount(val as MonkeyTypes.WordsModes);
     ManualRestart.set();
     TestLogic.restart();