diff --git a/src/RedisRateLimiting/Concurrency/RedisConcurrencyRateLimiter.cs b/src/RedisRateLimiting/Concurrency/RedisConcurrencyRateLimiter.cs
index 20871d8..e2d8ef8 100644
--- a/src/RedisRateLimiting/Concurrency/RedisConcurrencyRateLimiter.cs
+++ b/src/RedisRateLimiting/Concurrency/RedisConcurrencyRateLimiter.cs
@@ -76,6 +76,7 @@ protected override ValueTask<RateLimitLease> AcquireAsyncCore(int permitCount, C
 
         protected override RateLimitLease AttemptAcquireCore(int permitCount)
         {
+            // https://github.com/cristipufu/aspnetcore-redis-rate-limiting/issues/66
             return FailedLease;
         }
 
diff --git a/src/RedisRateLimiting/FixedWindow/RedisFixedWindowRateLimiter.cs b/src/RedisRateLimiting/FixedWindow/RedisFixedWindowRateLimiter.cs
index 2c1cdcf..b2998d2 100644
--- a/src/RedisRateLimiting/FixedWindow/RedisFixedWindowRateLimiter.cs
+++ b/src/RedisRateLimiting/FixedWindow/RedisFixedWindowRateLimiter.cs
@@ -62,6 +62,7 @@ protected override ValueTask<RateLimitLease> AcquireAsyncCore(int permitCount, C
 
         protected override RateLimitLease AttemptAcquireCore(int permitCount)
         {
+            // https://github.com/cristipufu/aspnetcore-redis-rate-limiting/issues/66
             return FailedLease;
         }
 
diff --git a/src/RedisRateLimiting/SlidingWindow/RedisSlidingWindowRateLimiter.cs b/src/RedisRateLimiting/SlidingWindow/RedisSlidingWindowRateLimiter.cs
index 8bbd4b6..53ad2ec 100644
--- a/src/RedisRateLimiting/SlidingWindow/RedisSlidingWindowRateLimiter.cs
+++ b/src/RedisRateLimiting/SlidingWindow/RedisSlidingWindowRateLimiter.cs
@@ -62,6 +62,7 @@ protected override ValueTask<RateLimitLease> AcquireAsyncCore(int permitCount, C
 
         protected override RateLimitLease AttemptAcquireCore(int permitCount)
         {
+            // https://github.com/cristipufu/aspnetcore-redis-rate-limiting/issues/66
             return FailedLease;
         }
 
diff --git a/src/RedisRateLimiting/TokenBucket/RedisTokenBucketRateLimiter.cs b/src/RedisRateLimiting/TokenBucket/RedisTokenBucketRateLimiter.cs
index 42ae207..875123f 100644
--- a/src/RedisRateLimiting/TokenBucket/RedisTokenBucketRateLimiter.cs
+++ b/src/RedisRateLimiting/TokenBucket/RedisTokenBucketRateLimiter.cs
@@ -67,6 +67,7 @@ protected override ValueTask<RateLimitLease> AcquireAsyncCore(int permitCount, C
 
         protected override RateLimitLease AttemptAcquireCore(int permitCount)
         {
+            // https://github.com/cristipufu/aspnetcore-redis-rate-limiting/issues/66
             return FailedLease;
         }
 
diff --git a/test/RedisRateLimiting.Tests/UnitTests/ConcurrencyUnitTests.cs b/test/RedisRateLimiting.Tests/UnitTests/ConcurrencyUnitTests.cs
index 6c3a2f2..fed46f9 100644
--- a/test/RedisRateLimiting.Tests/UnitTests/ConcurrencyUnitTests.cs
+++ b/test/RedisRateLimiting.Tests/UnitTests/ConcurrencyUnitTests.cs
@@ -48,9 +48,7 @@ public async Task ThrowsWhenAcquiringMoreThanLimit()
                     QueueLimit = 1,
                     ConnectionMultiplexerFactory = Fixture.ConnectionMultiplexerFactory,
                 });
-            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => limiter.AttemptAcquire(2));
-            Assert.Equal("permitCount", ex.ParamName);
-            ex = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(async () => await limiter.AcquireAsync(2));
+            var ex = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(async () => await limiter.AcquireAsync(2));
             Assert.Equal("permitCount", ex.ParamName);
         }
 
@@ -89,7 +87,7 @@ public async Task CanAcquireAsyncResource()
             Assert.Equal(1, stats.CurrentAvailablePermits);
         }
 
-        [Fact]
+        [Fact(Skip = "Sync always returns failed lease")]
         public void CanAcquireResource()
         {
             using var limiter = new RedisConcurrencyRateLimiter<string>(
@@ -161,7 +159,7 @@ public async Task FailsWhenQueuingMoreThanLimit()
                     ConnectionMultiplexerFactory = Fixture.ConnectionMultiplexerFactory,
                 });
 
-            using var lease = limiter.AttemptAcquire();
+            using var lease = await limiter.AcquireAsync();
             var wait = limiter.AcquireAsync();
 
             var failedLease = await limiter.AcquireAsync();
@@ -182,7 +180,7 @@ public async Task QueueAvailableAfterQueueLimitHitAndResourcesBecomeAvailable()
                     ConnectionMultiplexerFactory = Fixture.ConnectionMultiplexerFactory,
                 });
 
-            var lease = limiter.AttemptAcquire();
+            var lease = await limiter.AcquireAsync();
             var wait = limiter.AcquireAsync();
 
             await Task.Delay(1000);
diff --git a/test/RedisRateLimiting.Tests/UnitTests/FixedWindowUnitTests.cs b/test/RedisRateLimiting.Tests/UnitTests/FixedWindowUnitTests.cs
index d85d92f..0023868 100644
--- a/test/RedisRateLimiting.Tests/UnitTests/FixedWindowUnitTests.cs
+++ b/test/RedisRateLimiting.Tests/UnitTests/FixedWindowUnitTests.cs
@@ -57,9 +57,7 @@ public async Task ThrowsWhenAcquiringMoreThanLimit()
                     Window = TimeSpan.FromMinutes(1),
                     ConnectionMultiplexerFactory = Fixture.ConnectionMultiplexerFactory,
                 });
-            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => limiter.AttemptAcquire(2));
-            Assert.Equal("permitCount", ex.ParamName);
-            ex = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(async () => await limiter.AcquireAsync(2));
+            var ex = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(async () => await limiter.AcquireAsync(2));
             Assert.Equal("permitCount", ex.ParamName);
         }
 
diff --git a/test/RedisRateLimiting.Tests/UnitTests/SlidingWindowUnitTests.cs b/test/RedisRateLimiting.Tests/UnitTests/SlidingWindowUnitTests.cs
index 869317c..c1bf730 100644
--- a/test/RedisRateLimiting.Tests/UnitTests/SlidingWindowUnitTests.cs
+++ b/test/RedisRateLimiting.Tests/UnitTests/SlidingWindowUnitTests.cs
@@ -64,9 +64,7 @@ public async Task ThrowsWhenAcquiringMoreThanLimit()
                     Window = TimeSpan.FromMinutes(1),
                     ConnectionMultiplexerFactory = Fixture.ConnectionMultiplexerFactory,
                 });
-            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => limiter.AttemptAcquire(2));
-            Assert.Equal("permitCount", ex.ParamName);
-            ex = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(async () => await limiter.AcquireAsync(2));
+            var ex = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(async () => await limiter.AcquireAsync(2));
             Assert.Equal("permitCount", ex.ParamName);
         }
 
@@ -110,7 +108,7 @@ public async Task CanAcquireAsyncResourceWithSmallWindow()
                 new RedisSlidingWindowRateLimiterOptions
                 {
                     PermitLimit = 1,
-                    Window = TimeSpan.FromMilliseconds(100),
+                    Window = TimeSpan.FromMilliseconds(600),
                     ConnectionMultiplexerFactory = Fixture.ConnectionMultiplexerFactory,
                 });
 
@@ -120,7 +118,7 @@ public async Task CanAcquireAsyncResourceWithSmallWindow()
             using var lease2 = await limiter.AcquireAsync();
             Assert.False(lease2.IsAcquired);
 
-            await Task.Delay(TimeSpan.FromMilliseconds(100));
+            await Task.Delay(TimeSpan.FromMilliseconds(600));
 
             using var lease3 = await limiter.AcquireAsync();
             Assert.True(lease3.IsAcquired);
diff --git a/test/RedisRateLimiting.Tests/UnitTests/TokenBucketUnitTests.cs b/test/RedisRateLimiting.Tests/UnitTests/TokenBucketUnitTests.cs
index 0280650..b44c586 100644
--- a/test/RedisRateLimiting.Tests/UnitTests/TokenBucketUnitTests.cs
+++ b/test/RedisRateLimiting.Tests/UnitTests/TokenBucketUnitTests.cs
@@ -77,9 +77,7 @@ public async Task ThrowsWhenAcquiringMoreThanLimit()
                     ReplenishmentPeriod = TimeSpan.FromMinutes(1),
                     ConnectionMultiplexerFactory = Fixture.ConnectionMultiplexerFactory,
                 });
-            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => limiter.AttemptAcquire(2));
-            Assert.Equal("permitCount", ex.ParamName);
-            ex = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(async () => await limiter.AcquireAsync(2));
+            var ex = await Assert.ThrowsAsync<ArgumentOutOfRangeException>(async () => await limiter.AcquireAsync(2));
             Assert.Equal("permitCount", ex.ParamName);
         }