diff --git a/src/Tomlyn/Model/Accessors/DictionaryDynamicAccessor.cs b/src/Tomlyn/Model/Accessors/DictionaryDynamicAccessor.cs
index 3169d9f..9cf6979 100644
--- a/src/Tomlyn/Model/Accessors/DictionaryDynamicAccessor.cs
+++ b/src/Tomlyn/Model/Accessors/DictionaryDynamicAccessor.cs
@@ -232,7 +232,7 @@ public SlowDictionaryAccessor(DynamicModelReadContext context, Type dictionaryTy
         public override bool TryGetValue(object dictionary, object key, out object? value)
         {
             var parameters = new object?[2] { key, null };
-            var result = (bool)_methodTryGetValue.Invoke(dictionary, parameters);
+            var result = (bool)_methodTryGetValue.Invoke(dictionary, parameters)!;
             value = parameters[1];
             return result;
         }
diff --git a/src/Tomlyn/Model/Accessors/ListDynamicAccessor.cs b/src/Tomlyn/Model/Accessors/ListDynamicAccessor.cs
index 48df350..8964032 100644
--- a/src/Tomlyn/Model/Accessors/ListDynamicAccessor.cs
+++ b/src/Tomlyn/Model/Accessors/ListDynamicAccessor.cs
@@ -103,7 +103,7 @@ public int GetCount(object list)
             case TomlTableArray array:
                 return array.Count;
             default:
-                return (int)_propCount!.GetValue(list);
+                return (int)_propCount!.GetValue(list)!;
         }
     }
     
diff --git a/src/Tomlyn/Model/Accessors/StandardObjectDynamicAccessor.cs b/src/Tomlyn/Model/Accessors/StandardObjectDynamicAccessor.cs
index 7d955cf..1b63fc5 100644
--- a/src/Tomlyn/Model/Accessors/StandardObjectDynamicAccessor.cs
+++ b/src/Tomlyn/Model/Accessors/StandardObjectDynamicAccessor.cs
@@ -68,7 +68,7 @@ public override bool TryGetPropertyValue(SourceSpan span, object obj, string nam
 
     public override bool TrySetPropertyValue(SourceSpan span, object obj, string name, object? value)
     {
-        string? errorMessage = null;
+        string errorMessage = "Unknown error";
         try
         {
             if (_props.TryGetValue(name, out var prop))
@@ -92,7 +92,7 @@ public override bool TrySetPropertyValue(SourceSpan span, object obj, string nam
                                 errorMessage = $"The property value of type {value?.GetType().FullName} couldn't be converted to {prop.PropertyType} for the list property {TargetType.FullName}/{name}";
                             }
                         }
-                        else
+                        else if (listValue is not null)
                         {
                             foreach (var item in (IEnumerable)value)
                             {
diff --git a/src/Tomlyn/Model/SyntaxToModelTransform.cs b/src/Tomlyn/Model/SyntaxToModelTransform.cs
index 030aa08..274d825 100644
--- a/src/Tomlyn/Model/SyntaxToModelTransform.cs
+++ b/src/Tomlyn/Model/SyntaxToModelTransform.cs
@@ -517,9 +517,9 @@ private ReferenceEqualityComparer()
         {
         }
 
-#pragma warning disable CS0108, CS0114
-        public bool Equals(object x, object y)
-#pragma warning restore CS0108, CS0114
+#pragma warning disable CS0108
+        public bool Equals(object? x, object? y)
+#pragma warning restore CS0108
         {
             return ReferenceEquals(x, y);
         }
diff --git a/src/Tomlyn/Syntax/SyntaxValidator.cs b/src/Tomlyn/Syntax/SyntaxValidator.cs
index 994ec41..4ce92ad 100644
--- a/src/Tomlyn/Syntax/SyntaxValidator.cs
+++ b/src/Tomlyn/Syntax/SyntaxValidator.cs
@@ -378,10 +378,10 @@ public ObjectPath Clone()
                 return (ObjectPath) MemberwiseClone();
             }
 
-            public override bool Equals(object obj)
+            public override bool Equals(object? obj)
             {
-                var other = (ObjectPath) obj;
-                if (other.Count != Count) return false;
+                var other = obj as ObjectPath;
+                if (other?.Count != Count) return false;
                 if (other._hashCode != _hashCode) return false;
                 for (int i = 0; i < Count; i++)
                 {
diff --git a/src/Tomlyn/Syntax/TextPosition.cs b/src/Tomlyn/Syntax/TextPosition.cs
index 7329df9..147fe06 100644
--- a/src/Tomlyn/Syntax/TextPosition.cs
+++ b/src/Tomlyn/Syntax/TextPosition.cs
@@ -50,7 +50,7 @@ public bool Equals(TextPosition other)
             return Offset == other.Offset && Column == other.Column && Line == other.Line;
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (ReferenceEquals(null, obj)) return false;
             return obj is TextPosition && Equals((TextPosition) obj);
diff --git a/src/Tomlyn/TomlDateTime.cs b/src/Tomlyn/TomlDateTime.cs
index 7665566..fe06cd4 100644
--- a/src/Tomlyn/TomlDateTime.cs
+++ b/src/Tomlyn/TomlDateTime.cs
@@ -66,78 +66,78 @@ TypeCode IConvertible.GetTypeCode()
     }
 
     [ExcludeFromCodeCoverage]
-    bool IConvertible.ToBoolean(IFormatProvider provider)
+    bool IConvertible.ToBoolean(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    byte IConvertible.ToByte(IFormatProvider provider)
+    byte IConvertible.ToByte(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    char IConvertible.ToChar(IFormatProvider provider)
+    char IConvertible.ToChar(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    DateTime IConvertible.ToDateTime(IFormatProvider provider)
+    DateTime IConvertible.ToDateTime(IFormatProvider? provider)
     {
         return DateTime.DateTime;
     }
 
     [ExcludeFromCodeCoverage]
-    decimal IConvertible.ToDecimal(IFormatProvider provider)
+    decimal IConvertible.ToDecimal(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    double IConvertible.ToDouble(IFormatProvider provider)
+    double IConvertible.ToDouble(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    short IConvertible.ToInt16(IFormatProvider provider)
+    short IConvertible.ToInt16(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    int IConvertible.ToInt32(IFormatProvider provider)
+    int IConvertible.ToInt32(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    long IConvertible.ToInt64(IFormatProvider provider)
+    long IConvertible.ToInt64(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    sbyte IConvertible.ToSByte(IFormatProvider provider)
+    sbyte IConvertible.ToSByte(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    float IConvertible.ToSingle(IFormatProvider provider)
+    float IConvertible.ToSingle(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    string IConvertible.ToString(IFormatProvider provider)
+    string IConvertible.ToString(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
-    object IConvertible.ToType(Type conversionType, IFormatProvider provider)
+    object IConvertible.ToType(Type conversionType, IFormatProvider? provider)
     {
         if (conversionType == typeof(DateTime))
         {
@@ -165,19 +165,19 @@ object IConvertible.ToType(Type conversionType, IFormatProvider provider)
     }
 
     [ExcludeFromCodeCoverage]
-    ushort IConvertible.ToUInt16(IFormatProvider provider)
+    ushort IConvertible.ToUInt16(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    uint IConvertible.ToUInt32(IFormatProvider provider)
+    uint IConvertible.ToUInt32(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
 
     [ExcludeFromCodeCoverage]
-    ulong IConvertible.ToUInt64(IFormatProvider provider)
+    ulong IConvertible.ToUInt64(IFormatProvider? provider)
     {
         throw new NotSupportedException();
     }
diff --git a/src/Tomlyn/TomlModelOptions.cs b/src/Tomlyn/TomlModelOptions.cs
index 6313d58..057de40 100644
--- a/src/Tomlyn/TomlModelOptions.cs
+++ b/src/Tomlyn/TomlModelOptions.cs
@@ -130,6 +130,6 @@ private static object DefaultCreateInstanceImpl(Type type, ObjectKind kind)
             }
         }
 
-        return Activator.CreateInstance(type);
+        return Activator.CreateInstance(type) ?? throw new InvalidOperationException($"Failed to create an instance of type '{type.FullName}'");
     }
 }
\ No newline at end of file