diff --git a/src/Microsoft.OpenApi.Hidi/OpenApiService.cs b/src/Microsoft.OpenApi.Hidi/OpenApiService.cs
index 2cf1b01ad..ba8b84e0e 100644
--- a/src/Microsoft.OpenApi.Hidi/OpenApiService.cs
+++ b/src/Microsoft.OpenApi.Hidi/OpenApiService.cs
@@ -22,6 +22,7 @@
 using Microsoft.OpenApi.Services;
 using Microsoft.OpenApi.Validations;
 using Microsoft.OpenApi.Writers;
+using static Microsoft.OpenApi.Hidi.OpenApiSpecVersionHelper;
 using System.Threading;
 
 namespace Microsoft.OpenApi.Hidi
@@ -32,7 +33,7 @@ public static async Task<int> ProcessOpenApiDocument(
             string openapi,
             string csdl,
             FileInfo output,
-            OpenApiSpecVersion? version,
+            string? version,
             OpenApiFormat? format,
             LogLevel loglevel,
             bool inline,
@@ -63,14 +64,15 @@ CancellationToken cancellationToken
                 Stream stream;
                 OpenApiDocument document;
                 OpenApiFormat openApiFormat;
+                OpenApiSpecVersion openApiVersion;
                 var stopwatch = new Stopwatch();
 
                 if (!string.IsNullOrEmpty(csdl))
                 {
                     // Default to yaml and OpenApiVersion 3 during csdl to OpenApi conversion
                     openApiFormat = format ?? GetOpenApiFormat(csdl, logger);
-                    version ??= OpenApiSpecVersion.OpenApi3_0;
-
+                    openApiVersion = version == null ? OpenApiSpecVersion.OpenApi3_0 : TryParseOpenApiSpecVersion(version);
+                    
                     stream = await GetStream(csdl, logger, cancellationToken);
                     document = await ConvertCsdlToOpenApi(stream);
                 }
@@ -81,12 +83,12 @@ CancellationToken cancellationToken
                     // Parsing OpenAPI file
                     stopwatch.Start();
                     logger.LogTrace("Parsing OpenApi file");
-                    var result = new OpenApiStreamReader(new OpenApiReaderSettings
+                    var result = await new OpenApiStreamReader(new OpenApiReaderSettings
                     {
                         ReferenceResolution = resolveexternal ? ReferenceResolutionSetting.ResolveAllReferences : ReferenceResolutionSetting.ResolveLocalReferences,
                         RuleSet = ValidationRuleSet.GetDefaultRuleSet()
                     }
-                    ).ReadAsync(stream).GetAwaiter().GetResult();
+                    ).ReadAsync(stream);
 
                     document = result.OpenApiDocument;
                     stopwatch.Stop();
@@ -111,7 +113,7 @@ CancellationToken cancellationToken
                     }
 
                     openApiFormat = format ?? GetOpenApiFormat(openapi, logger);
-                    version ??= result.OpenApiDiagnostic.SpecificationVersion;
+                    openApiVersion = version == null ? TryParseOpenApiSpecVersion(version) : result.OpenApiDiagnostic.SpecificationVersion;
                 }
 
                 Func<string, OperationType?, OpenApiOperation, bool> predicate;
@@ -168,11 +170,10 @@ CancellationToken cancellationToken
                 logger.LogTrace("Serializing to OpenApi document using the provided spec version and writer");
 
                 stopwatch.Start();
-                document.Serialize(writer, (OpenApiSpecVersion)version);
+                document.Serialize(writer, openApiVersion);
                 stopwatch.Stop();
 
                 logger.LogTrace($"Finished serializing in {stopwatch.ElapsedMilliseconds}ms");
-
                 textWriter.Flush();
 
                 return 0;
@@ -187,7 +188,7 @@ CancellationToken cancellationToken
                 return 1;
             }            
         }
-
+        
         /// <summary>
         /// Converts CSDL to OpenAPI
         /// </summary>
diff --git a/src/Microsoft.OpenApi.Hidi/OpenApiSpecVersionHelper.cs b/src/Microsoft.OpenApi.Hidi/OpenApiSpecVersionHelper.cs
new file mode 100644
index 000000000..a78255be2
--- /dev/null
+++ b/src/Microsoft.OpenApi.Hidi/OpenApiSpecVersionHelper.cs
@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+using System;
+using System.Linq;
+
+namespace Microsoft.OpenApi.Hidi
+{
+    public static class OpenApiSpecVersionHelper
+    {
+        public static OpenApiSpecVersion TryParseOpenApiSpecVersion(string value)
+        {
+            if (string.IsNullOrEmpty(value))
+            {
+                throw new InvalidOperationException("Please provide a version");
+            }
+            var res = value.Split('.', StringSplitOptions.RemoveEmptyEntries).FirstOrDefault();
+
+            if (int.TryParse(res, out int result))
+            {
+
+                if (result >= 2 && result < 3)
+                {
+                    return OpenApiSpecVersion.OpenApi2_0;
+                }
+            }
+
+            return OpenApiSpecVersion.OpenApi3_0; // default
+        }
+    }
+}
diff --git a/src/Microsoft.OpenApi.Hidi/Program.cs b/src/Microsoft.OpenApi.Hidi/Program.cs
index f3d455e4a..24abb4a98 100644
--- a/src/Microsoft.OpenApi.Hidi/Program.cs
+++ b/src/Microsoft.OpenApi.Hidi/Program.cs
@@ -26,7 +26,7 @@ static async Task<int> Main(string[] args)
             var outputOption = new Option<FileInfo>("--output", () => new FileInfo("./output"), "The output directory path for the generated file.") { Arity = ArgumentArity.ZeroOrOne };
             outputOption.AddAlias("-o");
 
-            var versionOption = new Option<OpenApiSpecVersion?>("--version", "OpenAPI specification version");
+            var versionOption = new Option<string?>("--version", "OpenAPI specification version");
             versionOption.AddAlias("-v");
 
             var formatOption = new Option<OpenApiFormat?>("--format", "File format");
@@ -73,7 +73,7 @@ static async Task<int> Main(string[] args)
                 resolveExternalOption,
             };
 
-            transformCommand.SetHandler<string, string, FileInfo, OpenApiSpecVersion?, OpenApiFormat?, LogLevel, bool, bool, string, string, string, CancellationToken> (
+            transformCommand.SetHandler<string, string, FileInfo, string?, OpenApiFormat?, LogLevel, bool, bool, string, string, string, CancellationToken> (
                 OpenApiService.ProcessOpenApiDocument, descriptionOption, csdlOption, outputOption, versionOption, formatOption, logLevelOption, inlineOption, resolveExternalOption, filterByOperationIdsOption, filterByTagsOption, filterByCollectionOption);
 
             rootCommand.Add(transformCommand);