diff --git a/CliFx/ApplicationMetadata.cs b/CliFx/ApplicationMetadata.cs
index 5674724..0f778c1 100644
--- a/CliFx/ApplicationMetadata.cs
+++ b/CliFx/ApplicationMetadata.cs
@@ -28,7 +28,11 @@
         /// <summary>
         /// Initializes an instance of <see cref="ApplicationMetadata"/>.
         /// </summary>
-        public ApplicationMetadata(string title, string executableName, string versionText, string? description)
+        public ApplicationMetadata(
+            string title,
+            string executableName,
+            string versionText,
+            string? description)
         {
             Title = title;
             ExecutableName = executableName;
diff --git a/CliFx/Domain/CommandArgumentSchema.cs b/CliFx/Domain/CommandArgumentSchema.cs
index c2300e7..d9fab28 100644
--- a/CliFx/Domain/CommandArgumentSchema.cs
+++ b/CliFx/Domain/CommandArgumentSchema.cs
@@ -28,44 +28,52 @@ namespace CliFx.Domain
 
         private Type? TryGetEnumerableArgumentUnderlyingType() =>
             Property != null && Property.PropertyType != typeof(string)
-                ? Property.PropertyType.GetEnumerableUnderlyingType()
+                ? Property.PropertyType.TryGetEnumerableUnderlyingType()
                 : null;
 
         private object? ConvertScalar(string? value, Type targetType)
         {
             try
             {
-                // Custom conversion
+                // Custom conversion (always takes highest priority)
                 if (ConverterType != null)
                     return ConverterType.CreateInstance<IArgumentValueConverter>().ConvertFrom(value!);
 
-                // Primitive
+                // No conversion necessary
+                if (targetType == typeof(object) || targetType == typeof(string))
+                    return value;
+
+                // Bool conversion (special case)
+                if (targetType == typeof(bool))
+                    return string.IsNullOrWhiteSpace(value) || bool.Parse(value);
+
+                // Primitive conversion
                 var primitiveConverter = PrimitiveConverters.GetValueOrDefault(targetType);
-                if (primitiveConverter != null)
+                if (primitiveConverter != null && !string.IsNullOrWhiteSpace(value))
                     return primitiveConverter(value);
 
-                // Enum
-                if (targetType.IsEnum)
+                // Enum conversion
+                if (targetType.IsEnum && !string.IsNullOrWhiteSpace(value))
                     return Enum.Parse(targetType, value, true);
 
-                // Nullable
-                var nullableUnderlyingType = targetType.GetNullableUnderlyingType();
+                // Nullable<T> conversion
+                var nullableUnderlyingType = targetType.TryGetNullableUnderlyingType();
                 if (nullableUnderlyingType != null)
                     return !string.IsNullOrWhiteSpace(value)
                         ? ConvertScalar(value, nullableUnderlyingType)
                         : null;
 
-                // String-constructible
+                // String-constructible conversion
                 var stringConstructor = targetType.GetConstructor(new[] {typeof(string)});
                 if (stringConstructor != null)
                     return stringConstructor.Invoke(new object[] {value!});
 
-                // String-parseable (with format provider)
+                // String-parseable conversion (with format provider)
                 var parseMethodWithFormatProvider = targetType.TryGetStaticParseMethod(true);
                 if (parseMethodWithFormatProvider != null)
                     return parseMethodWithFormatProvider.Invoke(null, new object[] {value!, FormatProvider});
 
-                // String-parseable (without format provider)
+                // String-parseable conversion (without format provider)
                 var parseMethod = targetType.TryGetStaticParseMethod();
                 if (parseMethod != null)
                     return parseMethod.Invoke(null, new object[] {value!});
@@ -78,7 +86,10 @@ namespace CliFx.Domain
             throw CliFxException.CannotConvertToType(this, value, targetType);
         }
 
-        private object ConvertNonScalar(IReadOnlyList<string> values, Type targetEnumerableType, Type targetElementType)
+        private object ConvertNonScalar(
+            IReadOnlyList<string> values,
+            Type targetEnumerableType,
+            Type targetElementType)
         {
             var array = values
                 .Select(v => ConvertScalar(v, targetElementType))
@@ -133,7 +144,7 @@ namespace CliFx.Domain
                 return Array.Empty<string>();
 
             var underlyingType =
-                Property.PropertyType.GetNullableUnderlyingType() ??
+                Property.PropertyType.TryGetNullableUnderlyingType() ??
                 Property.PropertyType;
 
             // Enum
@@ -148,12 +159,9 @@ namespace CliFx.Domain
     {
         private static readonly IFormatProvider FormatProvider = CultureInfo.InvariantCulture;
 
-        private static readonly IReadOnlyDictionary<Type, Func<string?, object?>> PrimitiveConverters =
-            new Dictionary<Type, Func<string?, object?>>
+        private static readonly IReadOnlyDictionary<Type, Func<string, object?>> PrimitiveConverters =
+            new Dictionary<Type, Func<string, object?>>
             {
-                [typeof(object)] = v => v,
-                [typeof(string)] = v => v,
-                [typeof(bool)] = v => string.IsNullOrWhiteSpace(v) || bool.Parse(v),
                 [typeof(char)] = v => v.Single(),
                 [typeof(sbyte)] = v => sbyte.Parse(v, FormatProvider),
                 [typeof(byte)] = v => byte.Parse(v, FormatProvider),
diff --git a/CliFx/Domain/HelpTextWriter.cs b/CliFx/Domain/HelpTextWriter.cs
index f2b452b..5a05b95 100644
--- a/CliFx/Domain/HelpTextWriter.cs
+++ b/CliFx/Domain/HelpTextWriter.cs
@@ -385,7 +385,7 @@ namespace CliFx.Domain
             // Enumerable
             if (!(defaultValue is string) && defaultValue is IEnumerable defaultValues)
             {
-                var elementType = defaultValues.GetType().GetEnumerableUnderlyingType() ?? typeof(object);
+                var elementType = defaultValues.GetType().TryGetEnumerableUnderlyingType() ?? typeof(object);
 
                 // If the ToString() method is not overriden, the default value can't be formatted nicely
                 if (!elementType.IsToStringOverriden())
diff --git a/CliFx/Internal/Extensions/TypeExtensions.cs b/CliFx/Internal/Extensions/TypeExtensions.cs
index 6a05cdb..4c93a90 100644
--- a/CliFx/Internal/Extensions/TypeExtensions.cs
+++ b/CliFx/Internal/Extensions/TypeExtensions.cs
@@ -14,9 +14,9 @@ namespace CliFx.Internal.Extensions
 
         public static bool Implements(this Type type, Type interfaceType) => type.GetInterfaces().Contains(interfaceType);
 
-        public static Type? GetNullableUnderlyingType(this Type type) => Nullable.GetUnderlyingType(type);
+        public static Type? TryGetNullableUnderlyingType(this Type type) => Nullable.GetUnderlyingType(type);
 
-        public static Type? GetEnumerableUnderlyingType(this Type type)
+        public static Type? TryGetEnumerableUnderlyingType(this Type type)
         {
             if (type.IsPrimitive)
                 return null;
@@ -29,7 +29,7 @@ namespace CliFx.Internal.Extensions
 
             return type
                 .GetInterfaces()
-                .Select(GetEnumerableUnderlyingType)
+                .Select(TryGetEnumerableUnderlyingType)
                 .Where(t => t != null)
                 .OrderByDescending(t => t != typeof(object)) // prioritize more specific types
                 .FirstOrDefault();
diff --git a/CliFx/Internal/Polyfills.cs b/CliFx/Internal/Polyfills.cs
index 10f6987..daa3965 100644
--- a/CliFx/Internal/Polyfills.cs
+++ b/CliFx/Internal/Polyfills.cs
@@ -34,7 +34,7 @@ namespace System.Collections.Generic
         }
 
         public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dic, TKey key) =>
-            dic.TryGetValue(key, out var result) ? result! : default!;
+            dic.TryGetValue(key!, out var result) ? result! : default!;
     }
 }