diff --git a/src/SmartEnum/SmartEnum.cs b/src/SmartEnum/SmartEnum.cs
index f1a5f012..9ce44548 100644
--- a/src/SmartEnum/SmartEnum.cs
+++ b/src/SmartEnum/SmartEnum.cs
@@ -60,8 +60,7 @@ public abstract class SmartEnum<TEnum, TValue> :
                 var dictionary = new Dictionary<TValue, TEnum>(GetValueComparer());
                 foreach (var item in _enumOptions.Value)
                 {
-                    if (item._value != null && !dictionary.ContainsKey(item._value))
-                        dictionary.Add(item._value, item);
+                    dictionary.TryAdd(item._value, item);
                 }
                 return dictionary;
             });
@@ -106,6 +105,9 @@ protected SmartEnum(string name, TValue value)
             if (String.IsNullOrEmpty(name))
                 ThrowHelper.ThrowArgumentNullOrEmptyException(nameof(name));
 
+            if (value is null)
+                ThrowHelper.ThrowArgumentNullException(nameof(value));
+
             _name = name;
             _value = value;
         }
@@ -216,22 +218,12 @@ public static bool TryFromName(string name, bool ignoreCase, out TEnum result)
         /// <seealso cref="SmartEnum{TEnum, TValue}.TryFromValue(TValue, out TEnum)"/>
         public static TEnum FromValue(TValue value)
         {
-            TEnum result;
+            if (value is null)
+                ThrowHelper.ThrowArgumentNullException(nameof(value));
 
-            if (value != null)
-            {
-                if (!_fromValue.Value.TryGetValue(value, out result))
-                {
-                    ThrowHelper.ThrowValueNotFoundException<TEnum, TValue>(value);
-                }
-            }
-            else
+            if (!_fromValue.Value.TryGetValue(value, out var result))
             {
-                result = _enumOptions.Value.FirstOrDefault(x => x.Value == null);
-                if (result == null)
-                {
-                    ThrowHelper.ThrowValueNotFoundException<TEnum, TValue>(value);
-                }
+                ThrowHelper.ThrowValueNotFoundException<TEnum, TValue>(value);
             }
             return result;
         }
diff --git a/test/SmartEnum.UnitTests/SmartEnumStringFromValue.cs b/test/SmartEnum.UnitTests/SmartEnumStringFromValue.cs
index e82c8b59..7ce45063 100644
--- a/test/SmartEnum.UnitTests/SmartEnumStringFromValue.cs
+++ b/test/SmartEnum.UnitTests/SmartEnumStringFromValue.cs
@@ -23,18 +23,10 @@ public void ReturnsEnumGivenMatchingValue(string value, TestStringEnum expected)
         }
 
         [Fact]
-        public void ReturnsEnumGivenMatchingNullValue()
+        public void ThrowsGivenNonMatchingValue()
         {
-            var result = TestNullableStringEnum.FromValue(null);
+            var value = string.Empty;
 
-            result.Should().BeSameAs(TestNullableStringEnum.None);
-        }
-
-        [Theory]
-        [InlineData("invalid")]
-        [InlineData(null)]
-        public void ThrowsGivenNonMatchingValue(string value)
-        {
             Action action = () => TestStringEnum.FromValue(value);
 
             action.Should()
diff --git a/test/SmartEnum.UnitTests/TestEnum.cs b/test/SmartEnum.UnitTests/TestEnum.cs
index 95a02b5c..1735f15f 100644
--- a/test/SmartEnum.UnitTests/TestEnum.cs
+++ b/test/SmartEnum.UnitTests/TestEnum.cs
@@ -46,22 +46,12 @@ public class TestStringEnum : SmartEnum<TestStringEnum, string>
         public static readonly TestStringEnum One = new TestStringEnum(nameof(One), nameof(One));
         public static readonly TestStringEnum Two = new TestStringEnum(nameof(Two), nameof(Two));
         public static readonly TestStringEnum Three = new TestStringEnum(nameof(Three), nameof(Three));
-        public static readonly TestStringEnum Empty = new TestStringEnum(nameof(Empty), string.Empty);
 
         protected TestStringEnum(string name, string value) : base(name, value)
         {
         }
     }
 
-    public class TestNullableStringEnum : SmartEnum<TestNullableStringEnum, string>
-    {
-        public static readonly TestNullableStringEnum None = new TestNullableStringEnum(nameof(None), null);
-
-        protected TestNullableStringEnum(string name, string value) : base(name, value)
-        {
-        }
-    }
-
     public class TestBaseEnumWithDerivedValues : SmartEnum<TestBaseEnumWithDerivedValues>
     {
         protected TestBaseEnumWithDerivedValues(string name, int value) : base(name, value)