diff --git a/CliFx/Internal/Extensions.cs b/CliFx/Internal/Extensions.cs
index fe6baa6..9184c88 100644
--- a/CliFx/Internal/Extensions.cs
+++ b/CliFx/Internal/Extensions.cs
@@ -23,8 +23,8 @@ namespace CliFx.Internal
             return index < 0 ? s : s.Substring(0, index);
         }
 
-        public static StringBuilder AppendIfEmpty(this StringBuilder builder, char value) =>
-            builder.Length == 0 ? builder.Append(value) : builder;
+        public static StringBuilder AppendIfNotEmpty(this StringBuilder builder, char value) =>
+            builder.Length > 0 ? builder.Append(value) : builder;
 
         public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dic, TKey key) =>
             dic.TryGetValue(key, out var result) ? result : default;
diff --git a/CliFx/Models/CommandInput.cs b/CliFx/Models/CommandInput.cs
index afa5676..828ca8c 100644
--- a/CliFx/Models/CommandInput.cs
+++ b/CliFx/Models/CommandInput.cs
@@ -63,7 +63,7 @@ namespace CliFx.Models
 
             foreach (var option in Options)
             {
-                buffer.AppendIfEmpty(' ');
+                buffer.AppendIfNotEmpty(' ');
                 buffer.Append(option);
             }
 
diff --git a/CliFx/Models/CommandOptionInput.cs b/CliFx/Models/CommandOptionInput.cs
index 1f2ead7..9ad6447 100644
--- a/CliFx/Models/CommandOptionInput.cs
+++ b/CliFx/Models/CommandOptionInput.cs
@@ -54,7 +54,7 @@ namespace CliFx.Models
 
             foreach (var value in Values)
             {
-                buffer.AppendIfEmpty(' ');
+                buffer.AppendIfNotEmpty(' ');
 
                 var isEscaped = value.Contains(" ");
 
diff --git a/CliFx/Models/CommandSchema.cs b/CliFx/Models/CommandSchema.cs
index acb4059..79e043e 100644
--- a/CliFx/Models/CommandSchema.cs
+++ b/CliFx/Models/CommandSchema.cs
@@ -51,7 +51,7 @@ namespace CliFx.Models
 
             foreach (var option in Options)
             {
-                buffer.AppendIfEmpty(' ');
+                buffer.AppendIfNotEmpty(' ');
                 buffer.Append('[');
                 buffer.Append(option);
                 buffer.Append(']');