diff --git a/src/R3/Operators/MaxByMinByAsync.cs b/src/R3/Operators/MaxByMinByAsync.cs
index acf1ff43..04948db4 100644
--- a/src/R3/Operators/MaxByMinByAsync.cs
+++ b/src/R3/Operators/MaxByMinByAsync.cs
@@ -41,6 +41,7 @@ protected override void OnNextCore(T value)
         {
             hasValue = true;
             latestValue = value;
+            latestKey = keySelector(value);
             return;
         }
 
@@ -49,7 +50,6 @@ protected override void OnNextCore(T value)
         {
             latestValue = value;
             latestKey = key;
-            hasValue = true;
         }
     }
 
@@ -91,6 +91,7 @@ protected override void OnNextCore(T value)
         {
             hasValue = true;
             latestValue = value;
+            latestKey = keySelector(value);
             return;
         }
 
@@ -99,7 +100,6 @@ protected override void OnNextCore(T value)
         {
             latestValue = value;
             latestKey = key;
-            hasValue = true;
         }
     }
 
diff --git a/tests/R3.Tests/OperatorTests/MaxByTest.cs b/tests/R3.Tests/OperatorTests/MaxByTest.cs
index 06d98126..423d0e0b 100644
--- a/tests/R3.Tests/OperatorTests/MaxByTest.cs
+++ b/tests/R3.Tests/OperatorTests/MaxByTest.cs
@@ -3,11 +3,29 @@
 public class MaxByTest
 {
     [Fact]
-    public async Task MaxBy()
+    public async Task First()
+    {
+        var items = new[] { (3, 1), (2, 2), (1, 3) }.ToObservable();
+
+        var task = items.MaxByAsync(static x => x.Item1);
+        (await task).Should().Be((3, 1));
+    }
+
+    [Fact]
+    public async Task Last()
     {
         var items = new[] { (1, 3), (2, 2), (3, 1) }.ToObservable();
 
         var task = items.MaxByAsync(static x => x.Item1);
         (await task).Should().Be((3, 1));
     }
+
+    [Fact]
+    public async Task Midway()
+    {
+        var items = new[] { (2, 2), (3, 1), (1, 3) }.ToObservable();
+
+        var task = items.MaxByAsync(static x => x.Item1);
+        (await task).Should().Be((3, 1));
+    }
 }
diff --git a/tests/R3.Tests/OperatorTests/MaxTest.cs b/tests/R3.Tests/OperatorTests/MaxTest.cs
index f3ed355c..51d74fbf 100644
--- a/tests/R3.Tests/OperatorTests/MaxTest.cs
+++ b/tests/R3.Tests/OperatorTests/MaxTest.cs
@@ -11,8 +11,29 @@ public async Task One()
     [Fact]
     public async Task MultipleValue()
     {
-        var min = await new[] { 1, 10, 1, 3, 4, 6, 7, 4 }.ToObservable().MaxAsync();
-        min.Should().Be(10);
+        var max = await new[] { 1, 10, 1, 3, 4, 6, 7, 4 }.ToObservable().MaxAsync();
+        max.Should().Be(10);
+    }
+
+    [Fact]
+    public async Task First()
+    {
+        var max = await new[] { 10, 1, 3, 4, 6, 7, 5 }.ToObservable().MaxAsync();
+        max.Should().Be(10);
+    }
+
+    [Fact]
+    public async Task Last()
+    {
+        var max = await new[] { 6, 2, 7, 1, 3, 4, 10 }.ToObservable().MaxAsync();
+        max.Should().Be(10);
+    }
+
+    [Fact]
+    public async Task Midway()
+    {
+        var max = await new[] { 6, 2, 7, 10, 3, 4, 1 }.ToObservable().MaxAsync();
+        max.Should().Be(10);
     }
 
     [Fact]
diff --git a/tests/R3.Tests/OperatorTests/MinByTest.cs b/tests/R3.Tests/OperatorTests/MinByTest.cs
index 2bc1e217..dd6c4996 100644
--- a/tests/R3.Tests/OperatorTests/MinByTest.cs
+++ b/tests/R3.Tests/OperatorTests/MinByTest.cs
@@ -3,11 +3,29 @@
 public class MinByTest
 {
     [Fact]
-    public async Task MinBy()
+    public async Task First()
     {
         var items = new[] { (1, 3), (2, 2), (3, 1) }.ToObservable();
 
         var task = items.MinByAsync(static x => x.Item1);
         (await task).Should().Be((1, 3));
     }
+
+    [Fact]
+    public async Task Last()
+    {
+        var items = new[] { (3, 1), (2, 2), (1, 3) }.ToObservable();
+
+        var task = items.MinByAsync(static x => x.Item1);
+        (await task).Should().Be((1, 3));
+    }
+
+    [Fact]
+    public async Task Midway()
+    {
+        var items = new[] { (2, 2), (1, 3), (3, 1) }.ToObservable();
+
+        var task = items.MinByAsync(static x => x.Item1);
+        (await task).Should().Be((1, 3));
+    }
 }
diff --git a/tests/R3.Tests/OperatorTests/MinMaxTest.cs b/tests/R3.Tests/OperatorTests/MinMaxTest.cs
index 63bfa6ec..659cf65d 100644
--- a/tests/R3.Tests/OperatorTests/MinMaxTest.cs
+++ b/tests/R3.Tests/OperatorTests/MinMaxTest.cs
@@ -25,6 +25,27 @@ public async Task MultipleValues()
         (await source.MinMaxAsync(x => x * 10)).Should().Be((10, 100));
     }
 
+    [Fact]
+    public async Task First()
+    {
+        var minMax = await new[] { 1, 5, 3, 4, 6, 7, 10 }.ToObservable().MinMaxAsync();
+        minMax.Should().Be((1, 10));
+    }
+
+    [Fact]
+    public async Task Last()
+    {
+        var minMax = await new[] { 10, 2, 3, 4, 6, 7, 1 }.ToObservable().MinMaxAsync();
+        minMax.Should().Be((1, 10));
+    }
+
+    [Fact]
+    public async Task Midway()
+    {
+        var minMax = await new[] { 2, 4, 10, 3, 1, 6, 7, 5 }.ToObservable().MinMaxAsync();
+        minMax.Should().Be((1, 10));
+    }
+
     [Fact]
     public async Task Error()
     {
diff --git a/tests/R3.Tests/OperatorTests/MinTest.cs b/tests/R3.Tests/OperatorTests/MinTest.cs
index 5a9a22b3..f4aa8201 100644
--- a/tests/R3.Tests/OperatorTests/MinTest.cs
+++ b/tests/R3.Tests/OperatorTests/MinTest.cs
@@ -22,6 +22,27 @@ public async Task MultipleValue()
         min.Should().Be(1);
     }
 
+    [Fact]
+    public async Task First()
+    {
+        var min = await new[] { 1, 10, 3, 4, 6, 7, 5 }.ToObservable().MinAsync();
+        min.Should().Be(1);
+    }
+
+    [Fact]
+    public async Task Last()
+    {
+        var min = await new[] { 2, 10, 3, 4, 6, 7, 1 }.ToObservable().MinAsync();
+        min.Should().Be(1);
+    }
+
+    [Fact]
+    public async Task Midway()
+    {
+        var min = await new[] { 2, 10, 3, 4, 1, 6, 7, 5 }.ToObservable().MinAsync();
+        min.Should().Be(1);
+    }
+
     [Fact]
     public async Task Error()
     {