diff --git a/modules/teadsBidAdapter.js b/modules/teadsBidAdapter.js
index 08ae1854669..6d55aabbfb5 100644
--- a/modules/teadsBidAdapter.js
+++ b/modules/teadsBidAdapter.js
@@ -133,8 +133,8 @@ function getTimeToFirstByte(win) {
     performance.getEntriesByType('navigation')[0] &&
     performance.getEntriesByType('navigation')[0].responseStart &&
     performance.getEntriesByType('navigation')[0].requestStart &&
-    performance.getEntriesByType('navigation')[0].responseStart >= 0 &&
-    performance.getEntriesByType('navigation')[0].requestStart >= 0 &&
+    performance.getEntriesByType('navigation')[0].responseStart > 0 &&
+    performance.getEntriesByType('navigation')[0].requestStart > 0 &&
     Math.round(
       performance.getEntriesByType('navigation')[0].responseStart - performance.getEntriesByType('navigation')[0].requestStart
     );
@@ -146,8 +146,8 @@ function getTimeToFirstByte(win) {
   const ttfbWithTimingV1 = performance &&
     performance.timing.responseStart &&
     performance.timing.requestStart &&
-    performance.timing.responseStart >= 0 &&
-    performance.timing.requestStart >= 0 &&
+    performance.timing.responseStart > 0 &&
+    performance.timing.requestStart > 0 &&
     performance.timing.responseStart - performance.timing.requestStart;
 
   return ttfbWithTimingV1 ? ttfbWithTimingV1.toString() : '';
diff --git a/test/spec/modules/teadsBidAdapter_spec.js b/test/spec/modules/teadsBidAdapter_spec.js
index 17841b271d4..a6ae17ec8ff 100644
--- a/test/spec/modules/teadsBidAdapter_spec.js
+++ b/test/spec/modules/teadsBidAdapter_spec.js
@@ -200,8 +200,8 @@ describe('teadsBidAdapter', () => {
         performance.getEntriesByType('navigation')[0] &&
         performance.getEntriesByType('navigation')[0].responseStart &&
         performance.getEntriesByType('navigation')[0].requestStart &&
-        performance.getEntriesByType('navigation')[0].responseStart >= 0 &&
-        performance.getEntriesByType('navigation')[0].requestStart >= 0 &&
+        performance.getEntriesByType('navigation')[0].responseStart > 0 &&
+        performance.getEntriesByType('navigation')[0].requestStart > 0 &&
         Math.round(
           performance.getEntriesByType('navigation')[0].responseStart - performance.getEntriesByType('navigation')[0].requestStart
         );
@@ -211,9 +211,15 @@ describe('teadsBidAdapter', () => {
       if (ttfbExpectedV2) {
         expect(payload.timeToFirstByte).to.deep.equal(ttfbExpectedV2.toString());
       } else {
-        const ttfbExpectedV1 = performance.timing.responseStart - performance.timing.requestStart;
-
-        expect(payload.timeToFirstByte).to.deep.equal(ttfbExpectedV1.toString());
+        const ttfbWithTimingV1 = performance &&
+            performance.timing.responseStart &&
+            performance.timing.requestStart &&
+            performance.timing.responseStart > 0 &&
+            performance.timing.requestStart > 0 &&
+            performance.timing.responseStart - performance.timing.requestStart;
+        const ttfbExpectedV1 = ttfbWithTimingV1 ? ttfbWithTimingV1.toString() : '';
+
+        expect(payload.timeToFirstByte).to.deep.equal(ttfbExpectedV1);
       }
     });