diff --git a/src/libraries/System.Private.CoreLib/src/System/DateOnly.cs b/src/libraries/System.Private.CoreLib/src/System/DateOnly.cs
index 3c29ff3b84f04d..0f977d2b5368fc 100644
--- a/src/libraries/System.Private.CoreLib/src/System/DateOnly.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/DateOnly.cs
@@ -3,6 +3,7 @@
 
 using System.Diagnostics;
 using System.Globalization;
+using System.Diagnostics.CodeAnalysis;
 
 namespace System
 {
@@ -237,7 +238,7 @@ public int CompareTo(object? value)
         /// </summary>
         /// <param name="value">The object to compare to this instance.</param>
         /// <returns>true if value is an instance of DateOnly and equals the value of this instance; otherwise, false.</returns>
-        public override bool Equals(object? value) => value is DateOnly dateOnly && _dayNumber == dateOnly._dayNumber;
+        public override bool Equals([NotNullWhen(true)] object? value) => value is DateOnly dateOnly && _dayNumber == dateOnly._dayNumber;
 
         /// <summary>
         /// Returns the hash code for this instance.
diff --git a/src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/Label.cs b/src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/Label.cs
index a5c69737b9bcad..187933ea16f44d 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/Label.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/Label.cs
@@ -13,6 +13,8 @@
 **
 ===========================================================*/
 
+using System.Diagnostics.CodeAnalysis;
+
 namespace System.Reflection.Emit
 {
     // The Label class is an opaque representation of a label used by the
@@ -31,7 +33,7 @@ namespace System.Reflection.Emit
 
         public override int GetHashCode() => m_label;
 
-        public override bool Equals(object? obj) =>
+        public override bool Equals([NotNullWhen(true)] object? obj) =>
             obj is Label other && Equals(other);
 
         public bool Equals(Label obj) =>
diff --git a/src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/Opcode.cs b/src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/Opcode.cs
index cb40f1af0ef49c..2a44ed9e76d646 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/Opcode.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/Opcode.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Threading;
+using System.Diagnostics.CodeAnalysis;
 
 namespace System.Reflection.Emit
 {
@@ -108,7 +109,7 @@ public string? Name
             }
         }
 
-        public override bool Equals(object? obj) =>
+        public override bool Equals([NotNullWhen(true)] object? obj) =>
             obj is OpCode other && Equals(other);
 
         public bool Equals(OpCode obj) => obj.Value == Value;
diff --git a/src/libraries/System.Private.CoreLib/src/System/Reflection/Pointer.cs b/src/libraries/System.Private.CoreLib/src/System/Reflection/Pointer.cs
index ef8e82a9b0f18f..f6f09113c32219 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Reflection/Pointer.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Reflection/Pointer.cs
@@ -3,6 +3,7 @@
 
 using System.Diagnostics;
 using System.Runtime.Serialization;
+using System.Diagnostics.CodeAnalysis;
 
 namespace System.Reflection
 {
@@ -39,7 +40,7 @@ public static object Box(void* ptr, Type type)
             return ((Pointer)ptr)._ptr;
         }
 
-        public override unsafe bool Equals(object? obj)
+        public override unsafe bool Equals([NotNullWhen(true)] object? obj)
         {
             if (obj is Pointer pointer)
             {
diff --git a/src/libraries/System.Private.CoreLib/src/System/TimeOnly.cs b/src/libraries/System.Private.CoreLib/src/System/TimeOnly.cs
index 1ded5053f25339..74d08f67513c7e 100644
--- a/src/libraries/System.Private.CoreLib/src/System/TimeOnly.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/TimeOnly.cs
@@ -3,6 +3,7 @@
 
 using System.Diagnostics;
 using System.Globalization;
+using System.Diagnostics.CodeAnalysis;
 
 namespace System
 {
@@ -307,7 +308,7 @@ public int CompareTo(object? value)
         /// </summary>
         /// <param name="value">The object to compare to this instance.</param>
         /// <returns>true if value is an instance of TimeOnly and equals the value of this instance; otherwise, false.</returns>
-        public override bool Equals(object? value) => value is TimeOnly timeOnly && _ticks == timeOnly._ticks;
+        public override bool Equals([NotNullWhen(true)] object? value) => value is TimeOnly timeOnly && _ticks == timeOnly._ticks;
 
         /// <summary>
         /// Returns the hash code for this instance.
diff --git a/src/libraries/System.Reflection.Emit.ILGeneration/ref/System.Reflection.Emit.ILGeneration.cs b/src/libraries/System.Reflection.Emit.ILGeneration/ref/System.Reflection.Emit.ILGeneration.cs
index ef1ede20347e4d..449916fb2a442f 100644
--- a/src/libraries/System.Reflection.Emit.ILGeneration/ref/System.Reflection.Emit.ILGeneration.cs
+++ b/src/libraries/System.Reflection.Emit.ILGeneration/ref/System.Reflection.Emit.ILGeneration.cs
@@ -59,7 +59,7 @@ public virtual void UsingNamespace(string usingNamespace) { }
     public readonly partial struct Label : System.IEquatable<System.Reflection.Emit.Label>
     {
         private readonly int _dummyPrimitive;
-        public override bool Equals(object? obj) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? obj) { throw null; }
         public bool Equals(System.Reflection.Emit.Label obj) { throw null; }
         public override int GetHashCode() { throw null; }
         public static bool operator ==(System.Reflection.Emit.Label a, System.Reflection.Emit.Label b) { throw null; }
diff --git a/src/libraries/System.Reflection.Primitives/ref/System.Reflection.Primitives.cs b/src/libraries/System.Reflection.Primitives/ref/System.Reflection.Primitives.cs
index 225eb1558951af..c14ab12ccdc2ed 100644
--- a/src/libraries/System.Reflection.Primitives/ref/System.Reflection.Primitives.cs
+++ b/src/libraries/System.Reflection.Primitives/ref/System.Reflection.Primitives.cs
@@ -30,7 +30,7 @@ public enum FlowControl
         public System.Reflection.Emit.StackBehaviour StackBehaviourPop { get { throw null; } }
         public System.Reflection.Emit.StackBehaviour StackBehaviourPush { get { throw null; } }
         public short Value { get { throw null; } }
-        public override bool Equals(object? obj) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? obj) { throw null; }
         public bool Equals(System.Reflection.Emit.OpCode obj) { throw null; }
         public override int GetHashCode() { throw null; }
         public static bool operator ==(System.Reflection.Emit.OpCode a, System.Reflection.Emit.OpCode b) { throw null; }
diff --git a/src/libraries/System.Runtime/ref/System.Runtime.cs b/src/libraries/System.Runtime/ref/System.Runtime.cs
index a78df2b946602a..005a751d646215 100644
--- a/src/libraries/System.Runtime/ref/System.Runtime.cs
+++ b/src/libraries/System.Runtime/ref/System.Runtime.cs
@@ -1328,7 +1328,7 @@ public static partial class Convert
         public int CompareTo(System.DateOnly value) { throw null; }
         public int CompareTo(object? value)  { throw null; }
         public bool Equals(System.DateOnly value) { throw null; }
-        public override bool Equals(object? value) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? value) { throw null; }
         public override int GetHashCode() { throw null; }
         public static System.DateOnly Parse(System.ReadOnlySpan<char> s, System.IFormatProvider? provider = default, System.Globalization.DateTimeStyles style = System.Globalization.DateTimeStyles.None) { throw null; }
         public static System.DateOnly ParseExact(System.ReadOnlySpan<char> s, System.ReadOnlySpan<char> format, System.IFormatProvider? provider = default, System.Globalization.DateTimeStyles style = System.Globalization.DateTimeStyles.None) { throw null; }
@@ -3845,7 +3845,7 @@ public ThreadStaticAttribute() { }
         public int CompareTo(System.TimeOnly value) { throw null; }
         public int CompareTo(object? value) { throw null; }
         public bool Equals(System.TimeOnly value) { throw null; }
-        public override bool Equals(object? value) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? value) { throw null; }
         public override int GetHashCode() { throw null; }
         public static System.TimeOnly Parse(System.ReadOnlySpan<char> s, System.IFormatProvider? provider = default, System.Globalization.DateTimeStyles style = System.Globalization.DateTimeStyles.None) { throw null; }
         public static System.TimeOnly ParseExact(System.ReadOnlySpan<char> s, System.ReadOnlySpan<char> format, System.IFormatProvider? provider = default, System.Globalization.DateTimeStyles style = System.Globalization.DateTimeStyles.None) { throw null; }
@@ -8842,7 +8842,7 @@ internal Pointer() { }
         public unsafe static object Box(void* ptr, System.Type type) { throw null; }
         void System.Runtime.Serialization.ISerializable.GetObjectData(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context) { }
         public unsafe static void* Unbox(object ptr) { throw null; }
-        public override bool Equals(object? obj) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? obj) { throw null; }
         public override int GetHashCode() { throw null; }
     }
     [System.FlagsAttribute]