diff --git a/src-examples/ProxyInterfaceConsumer/Address.cs b/src-examples/ProxyInterfaceConsumer/Address.cs
index c4db154..0d15551 100644
--- a/src-examples/ProxyInterfaceConsumer/Address.cs
+++ b/src-examples/ProxyInterfaceConsumer/Address.cs
@@ -1,4 +1,4 @@
-namespace ProxyInterfaceConsumer
+namespace DifferentNamespace
 {
     public class Address
     {
diff --git a/src-examples/ProxyInterfaceConsumer/IAddress.cs b/src-examples/ProxyInterfaceConsumer/IAddress.cs
index d44b0f6..70b8fcb 100644
--- a/src-examples/ProxyInterfaceConsumer/IAddress.cs
+++ b/src-examples/ProxyInterfaceConsumer/IAddress.cs
@@ -1,6 +1,10 @@
-namespace ProxyInterfaceConsumer
+using DifferentNamespace;
+using System;
+using System.Linq;
+
+namespace ProxyInterfaceConsumer
 {
-    // [ProxyInterfaceGenerator.Proxy(typeof(ProxyInterfaceConsumer.Address))]
+    [ProxyInterfaceGenerator.Proxy(typeof(Address))]
     public partial interface IAddress
     {
     }
diff --git a/src-examples/ProxyInterfaceConsumer/Person.cs b/src-examples/ProxyInterfaceConsumer/Person.cs
index 84efcc1..09c0e34 100644
--- a/src-examples/ProxyInterfaceConsumer/Person.cs
+++ b/src-examples/ProxyInterfaceConsumer/Person.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using DifferentNamespace;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 
 namespace ProxyInterfaceConsumer
diff --git a/src/ProxyInterfaceSourceGenerator/Compatibility/NullableAttributes.cs b/src/ProxyInterfaceSourceGenerator/Compatibility/NullableAttributes.cs
new file mode 100644
index 0000000..82dfeb2
--- /dev/null
+++ b/src/ProxyInterfaceSourceGenerator/Compatibility/NullableAttributes.cs
@@ -0,0 +1,18 @@
+// https://stackoverflow.com/questions/61573959/how-to-resolve-error-notnullwhen-attribute-is-inaccessible-due-to-its-protectio
+
+namespace System.Diagnostics.CodeAnalysis
+{
+    /// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter will not be null even if the corresponding type allows it.</summary>
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    internal sealed class NotNullWhenAttribute : Attribute
+    {
+        /// <summary>Initializes the attribute with the specified return value condition.</summary>
+        /// <param name="returnValue">
+        /// The return value condition. If the method returns this value, the associated parameter will not be null.
+        /// </param>
+        public NotNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;
+
+        /// <summary>Gets the return value condition.</summary>
+        public bool ReturnValue { get; }
+    }
+}
\ No newline at end of file
diff --git a/src/ProxyInterfaceSourceGenerator/Extensions/SyntaxNodeUtils.cs b/src/ProxyInterfaceSourceGenerator/Extensions/SyntaxNodeUtils.cs
index fb2c780..a8bed5e 100644
--- a/src/ProxyInterfaceSourceGenerator/Extensions/SyntaxNodeUtils.cs
+++ b/src/ProxyInterfaceSourceGenerator/Extensions/SyntaxNodeUtils.cs
@@ -1,11 +1,12 @@
 using Microsoft.CodeAnalysis;
+using System.Diagnostics.CodeAnalysis;
 
 namespace ProxyInterfaceSourceGenerator.Extensions
 {
     internal static class SyntaxNodeUtils
     {
         // https://stackoverflow.com/questions/20458457/getting-class-fullname-including-namespace-from-roslyn-classdeclarationsyntax
-        public static bool TryGetParentSyntax<T>(this SyntaxNode? syntaxNode, out T? result) where T : SyntaxNode
+        public static bool TryGetParentSyntax<T>(this SyntaxNode? syntaxNode, [NotNullWhen(true)] out T? result) where T : SyntaxNode
         {
             result = null;
 
@@ -25,7 +26,7 @@ namespace ProxyInterfaceSourceGenerator.Extensions
 
                 if (syntaxNode.GetType() == typeof(T))
                 {
-                    result = syntaxNode as T;
+                    result = (T)syntaxNode;
                     return true;
                 }
 
diff --git a/src/ProxyInterfaceSourceGenerator/FileGenerators/BaseGenerator.cs b/src/ProxyInterfaceSourceGenerator/FileGenerators/BaseGenerator.cs
index 36bcec8..a570541 100644
--- a/src/ProxyInterfaceSourceGenerator/FileGenerators/BaseGenerator.cs
+++ b/src/ProxyInterfaceSourceGenerator/FileGenerators/BaseGenerator.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using Microsoft.CodeAnalysis;
 
@@ -67,16 +68,28 @@ namespace ProxyInterfaceSourceGenerator.FileGenerators
             return typeSymbolAsString;
         }
 
-        protected INamedTypeSymbol GetNamedTypeSymbolByFullName(string fullName)
+        protected INamedTypeSymbol GetNamedTypeSymbolByFullName(string name, IEnumerable<string>? usings = null)
         {
             // The GetTypeByMetadataName method returns null if no type matches the full name or if 2 or more types (in different assemblies) match the full name.
-            var symbol = _context.GeneratorExecutionContext.Compilation.GetTypeByMetadataName(fullName);
-            if (symbol is null)
-            {
-                throw new Exception($"The type '{fullName}' is not found.");
+            var symbol = _context.GeneratorExecutionContext.Compilation.GetTypeByMetadataName(name);
+            if (symbol is not null)
+            {
+                return symbol;
+            }
+
+            if (usings is not null)
+            {
+                foreach (var @using in usings)
+                {
+                    symbol = _context.GeneratorExecutionContext.Compilation.GetTypeByMetadataName($"{@using}.{name}");
+                    if (symbol is not null)
+                    {
+                        return symbol;
+                    }
+                }
             }
 
-            return symbol;
+            throw new Exception($"The type '{name}' is not found.");
         }
     }
 }
\ No newline at end of file
diff --git a/src/ProxyInterfaceSourceGenerator/FileGenerators/PartialInterfacesGenerator.cs b/src/ProxyInterfaceSourceGenerator/FileGenerators/PartialInterfacesGenerator.cs
index 301dc4a..ee422dc 100644
--- a/src/ProxyInterfaceSourceGenerator/FileGenerators/PartialInterfacesGenerator.cs
+++ b/src/ProxyInterfaceSourceGenerator/FileGenerators/PartialInterfacesGenerator.cs
@@ -26,7 +26,7 @@ namespace ProxyInterfaceSourceGenerator.FileGenerators
 
         private FileData GenerateFile(ProxyData pd)
         {
-            var targetClassSymbol = GetNamedTypeSymbolByFullName(pd.TypeName);
+            var targetClassSymbol = GetNamedTypeSymbolByFullName(pd.TypeName, pd.Usings);
             var interfaceName = targetClassSymbol.ResolveInterfaceNameWithOptionalTypeConstraints(pd.InterfaceName);
 
             var file = new FileData(
diff --git a/src/ProxyInterfaceSourceGenerator/FileGenerators/ProxyClassesGenerator.cs b/src/ProxyInterfaceSourceGenerator/FileGenerators/ProxyClassesGenerator.cs
index 202731a..fdb69ac 100644
--- a/src/ProxyInterfaceSourceGenerator/FileGenerators/ProxyClassesGenerator.cs
+++ b/src/ProxyInterfaceSourceGenerator/FileGenerators/ProxyClassesGenerator.cs
@@ -26,7 +26,7 @@ namespace ProxyInterfaceSourceGenerator.FileGenerators
 
         private FileData GenerateFile(ProxyData pd)
         {
-            var targetClassSymbol = GetNamedTypeSymbolByFullName(pd.TypeName);
+            var targetClassSymbol = GetNamedTypeSymbolByFullName(pd.TypeName, pd.Usings);
             var interfaceName = targetClassSymbol.ResolveInterfaceNameWithOptionalTypeConstraints(pd.InterfaceName);
             var className = targetClassSymbol.ResolveProxyClassName();
             var constructorName = $"{targetClassSymbol.Name}Proxy";
diff --git a/src/ProxyInterfaceSourceGenerator/SyntaxReceiver/ProxyData.cs b/src/ProxyInterfaceSourceGenerator/SyntaxReceiver/ProxyData.cs
index 411b5c7..9729900 100644
--- a/src/ProxyInterfaceSourceGenerator/SyntaxReceiver/ProxyData.cs
+++ b/src/ProxyInterfaceSourceGenerator/SyntaxReceiver/ProxyData.cs
@@ -1,6 +1,8 @@
-namespace ProxyInterfaceSourceGenerator.SyntaxReceiver
+using System.Collections.Generic;
+
+namespace ProxyInterfaceSourceGenerator.SyntaxReceiver
 {
-    internal record ProxyData(string Namespace, string InterfaceName, string RawTypeName, string TypeName, bool ProxyAll)
+    internal record ProxyData(string Namespace, string InterfaceName, string RawTypeName, string TypeName, List<string> Usings,  bool ProxyAll)
     {
         public string FileName => TypeName.Replace('.', '_').Replace('`', '_');
     }
diff --git a/src/ProxyInterfaceSourceGenerator/SyntaxReceiver/ProxySyntaxReceiver.cs b/src/ProxyInterfaceSourceGenerator/SyntaxReceiver/ProxySyntaxReceiver.cs
index 7b9e6a8..0047e60 100644
--- a/src/ProxyInterfaceSourceGenerator/SyntaxReceiver/ProxySyntaxReceiver.cs
+++ b/src/ProxyInterfaceSourceGenerator/SyntaxReceiver/ProxySyntaxReceiver.cs
@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
@@ -20,9 +21,9 @@ namespace ProxyInterfaceSourceGenerator.SyntaxReceiver
             }
         }
 
-        private static bool TryGet(InterfaceDeclarationSyntax interfaceDeclarationSyntax, out ProxyData data)
+        private static bool TryGet(InterfaceDeclarationSyntax interfaceDeclarationSyntax, [NotNullWhen(true)] out ProxyData? data)
         {
-            data = new(string.Empty, string.Empty, string.Empty, string.Empty, false);
+            data = null;
 
             if (interfaceDeclarationSyntax.Modifiers.Select(m => m.ToString()).Except(Modifiers).Count() != 0)
             {
@@ -42,27 +43,39 @@ namespace ProxyInterfaceSourceGenerator.SyntaxReceiver
                 return false;
             }
 
+            var usings = new List<string>();
+
             string ns = string.Empty;
-            if (SyntaxNodeUtils.TryGetParentSyntax(interfaceDeclarationSyntax, out NamespaceDeclarationSyntax namespaceDeclarationSyntax))
+            if (SyntaxNodeUtils.TryGetParentSyntax(interfaceDeclarationSyntax, out NamespaceDeclarationSyntax? namespaceDeclarationSyntax))
             {
                 ns = namespaceDeclarationSyntax.Name.ToString();
+                usings.Add(ns);
+            }
+                        
+            if (SyntaxNodeUtils.TryGetParentSyntax(interfaceDeclarationSyntax, out CompilationUnitSyntax? cc))
+            {
+                foreach (var @using in cc.Usings)
+                {
+                    usings.Add(@using.Name.ToString());
+                }
             }
 
-            string rawTypename = ((TypeOfExpressionSyntax)argumentList.Arguments[0].Expression).Type.ToString();
+            string rawTypeName = ((TypeOfExpressionSyntax)argumentList.Arguments[0].Expression).Type.ToString();
 
             data = new
             (
                 ns,
                 interfaceDeclarationSyntax.Identifier.ToString(),
-                rawTypename,
-                ResolveType(rawTypename),
+                rawTypeName,
+                ConvertTypeName(rawTypeName),
+                usings,
                 false //bool.Parse(argumentList.Arguments[1].Expression.GetText().ToString())
             );
 
             return true;
         }
 
-        private static string ResolveType(string typeName)
+        private static string ConvertTypeName(string typeName)
         {
             return !(typeName.Contains('<') && typeName.Contains('>')) ?
                 typeName :