diff --git a/AutoRest/AutoRest.Core.Tests/CodeGeneratorsTests.cs b/AutoRest/AutoRest.Core.Tests/CodeGeneratorsTests.cs
index c58c81e4e6..8cadb3f641 100644
--- a/AutoRest/AutoRest.Core.Tests/CodeGeneratorsTests.cs
+++ b/AutoRest/AutoRest.Core.Tests/CodeGeneratorsTests.cs
@@ -86,8 +86,11 @@ public void OutputToSingleFile()
             };
 
             string path = Path.Combine(settings.OutputDirectory, "test.file.cs");
+            string existingContents = "this is dummy";
+            _fileSystem.VirtualStore[path] = new StringBuilder(existingContents);
             var codeGenerator = new SampleCodeGenerator(settings);
             codeGenerator.Generate(new ServiceClient()).GetAwaiter().GetResult();
+            Assert.DoesNotContain(existingContents, _fileSystem.VirtualStore[path].ToString());
             Assert.Equal(4, _fileSystem.VirtualStore.Count);
             Assert.True(_fileSystem.VirtualStore.ContainsKey(path));
             Assert.True(_fileSystem.VirtualStore.ContainsKey("AutoRest.json"));
diff --git a/AutoRest/AutoRest.Core/CodeGenerator.cs b/AutoRest/AutoRest.Core/CodeGenerator.cs
index 8efb1c0311..57dbecb697 100644
--- a/AutoRest/AutoRest.Core/CodeGenerator.cs
+++ b/AutoRest/AutoRest.Core/CodeGenerator.cs
@@ -16,6 +16,7 @@ namespace Microsoft.Rest.Generator
     public abstract class CodeGenerator
     {
         public const string EnumObject = "x-ms-enum";
+        private bool firstTimeWriteSingleFile = true;
 
         protected CodeGenerator(Settings settings)
         {
@@ -99,7 +100,7 @@ public async Task Write(ITemplate template, string fileName)
         /// <returns></returns>
         public async Task Write(string template, string fileName)
         {
-            string relativeFilePath = null;
+            string filePath = null;
 
             if (Settings.OutputFileName != null)
             {
@@ -110,17 +111,19 @@ public async Task Write(string template, string fileName)
                     ErrorManager.ThrowErrors();
                 }
                 
-                relativeFilePath = Settings.OutputFileName;  
+                filePath = Path.Combine(Settings.OutputDirectory, Settings.OutputFileName);
+
+                if (firstTimeWriteSingleFile)
+                {
+                    // for SingleFileGeneration clean the file before writing only if its the first time
+                    Settings.FileSystem.DeleteFile(filePath);
+                    firstTimeWriteSingleFile = false;
+                }
             }
             else
             {
-                relativeFilePath = fileName;
-            }
-            string filePath = Path.Combine(Settings.OutputDirectory, relativeFilePath);
-
-            // cleans file before writing unless single file
-            if (!(Settings.OutputFileName != null && IsSingleFileGenerationSupported))
-            {
+                filePath = Path.Combine(Settings.OutputDirectory, fileName);
+                // cleans file before writing
                 Settings.FileSystem.DeleteFile(filePath);
             }
             // Make sure the directory exist