diff --git a/internal/urlutil/url.go b/internal/urlutil/url.go
index 8920dbe19..6c4d8a25f 100644
--- a/internal/urlutil/url.go
+++ b/internal/urlutil/url.go
@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"net/url"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/pomerium/pomerium/internal/cryptutil"
@@ -65,18 +66,35 @@ func DeepCopy(u *url.URL) (*url.URL, error) {
 	return ParseAndValidateURL(u.String())
 }
 
-// testTimeNow can be used in tests to set a specific int64 time
-var testTimeNow int64
+var mockNow testTime
+
+// testTime is safe to use concurrently.
+type testTime struct {
+	sync.Mutex
+	mockNow int64
+}
+
+func (tt *testTime) setNow(n int64) {
+	tt.Lock()
+	tt.mockNow = n
+	tt.Unlock()
+}
+
+func (tt *testTime) now() int64 {
+	tt.Lock()
+	defer tt.Unlock()
+	return tt.mockNow
+}
 
 // timestamp returns the current timestamp, in seconds.
 //
 // For testing purposes, the function that generates the timestamp can be
 // overridden. If not set, it will return time.Now().UTC().Unix().
 func timestamp() int64 {
-	if testTimeNow == 0 {
+	if mockNow.now() == 0 {
 		return time.Now().UTC().Unix()
 	}
-	return testTimeNow
+	return mockNow.now()
 }
 
 // SignedRedirectURL takes a destination URL and adds redirect_uri to it's
diff --git a/internal/urlutil/url_test.go b/internal/urlutil/url_test.go
index 95f77d8a8..5935fc86c 100644
--- a/internal/urlutil/url_test.go
+++ b/internal/urlutil/url_test.go
@@ -122,7 +122,7 @@ func TestSignedRedirectURL(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			testTimeNow = tt.mockedTime
+			mockNow.setNow(tt.mockedTime)
 			got := SignedRedirectURL(tt.key, tt.destination, tt.urlToSign)
 			if diff := cmp.Diff(got, tt.want); diff != "" {
 				t.Errorf("SignedRedirectURL() = diff %v", diff)
@@ -142,7 +142,7 @@ func Test_timestamp(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			testTimeNow = tt.dontWant
+			mockNow.setNow(tt.dontWant)
 			if got := timestamp(); got == tt.dontWant {
 				t.Errorf("timestamp() = %v, dontWant %v", got, tt.dontWant)
 			}