diff --git a/src/Microsoft.VisualStudio.SolutionPersistence/Errors.Designer.cs b/src/Microsoft.VisualStudio.SolutionPersistence/Errors.Designer.cs
index 95ecaea..d4a76b4 100644
--- a/src/Microsoft.VisualStudio.SolutionPersistence/Errors.Designer.cs
+++ b/src/Microsoft.VisualStudio.SolutionPersistence/Errors.Designer.cs
@@ -226,15 +226,6 @@ internal static string InvalidProjectReference_Args1 {
             }
         }
         
-        /// <summary>
-        ///   Looks up a localized string similar to Missing or invalid project type guid..
-        /// </summary>
-        internal static string InvalidProjectType {
-            get {
-                return ResourceManager.GetString("InvalidProjectType", resourceCulture);
-            }
-        }
-        
         /// <summary>
         ///   Looks up a localized string similar to ProjectType &apos;{0}&apos; not found..
         /// </summary>
diff --git a/src/Microsoft.VisualStudio.SolutionPersistence/Errors.resx b/src/Microsoft.VisualStudio.SolutionPersistence/Errors.resx
index fb39ab1..9b902f9 100644
--- a/src/Microsoft.VisualStudio.SolutionPersistence/Errors.resx
+++ b/src/Microsoft.VisualStudio.SolutionPersistence/Errors.resx
@@ -129,10 +129,6 @@
     <value>Missing or invalid scope.</value>
     <comment>Error message</comment>
   </data>
-  <data name="InvalidProjectType" xml:space="preserve">
-    <value>Missing or invalid project type guid.</value>
-    <comment>Error message</comment>
-  </data>
   <data name="SyntaxError" xml:space="preserve">
     <value>Syntax error.</value>
     <comment>Error message</comment>
diff --git a/src/Microsoft.VisualStudio.SolutionPersistence/Serializer/SlnV12/SlnFileV12Serializer.Reader.cs b/src/Microsoft.VisualStudio.SolutionPersistence/Serializer/SlnV12/SlnFileV12Serializer.Reader.cs
index be07021..9643bfa 100644
--- a/src/Microsoft.VisualStudio.SolutionPersistence/Serializer/SlnV12/SlnFileV12Serializer.Reader.cs
+++ b/src/Microsoft.VisualStudio.SolutionPersistence/Serializer/SlnV12/SlnFileV12Serializer.Reader.cs
@@ -525,7 +525,11 @@ private SolutionItemModel ReadProjectInfo(SolutionModel solution, ref StringToke
             StringSpan projectType = tokenizer.NextToken(SlnConstants.ProjectSeparators);
 
             // but it must end with [sep]) ... checked later.
-            this.SolutionAssert(Guid.TryParse(projectType.ToString(), out Guid projectTypeId), Errors.InvalidProjectType);
+            if (!Guid.TryParse(projectType.ToString(), out Guid projectTypeId))
+            {
+                projectTypeId = Guid.Empty;
+                this.tarnished = true;
+            }
 
             // this just skips up to Display's name "App1" first quote, position at 'A". The TrimStart is extension to allow spaces before ')';
             // and yes, any characters are allowed for example // Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "App1", valid bad format :P "App1\App1.csproj",
diff --git a/test/Microsoft.VisualStudio.SolutionPersistence.Tests/Serialization/InvalidSolutions.cs b/test/Microsoft.VisualStudio.SolutionPersistence.Tests/Serialization/InvalidSolutions.cs
index 6a36ff3..39a344a 100644
--- a/test/Microsoft.VisualStudio.SolutionPersistence.Tests/Serialization/InvalidSolutions.cs
+++ b/test/Microsoft.VisualStudio.SolutionPersistence.Tests/Serialization/InvalidSolutions.cs
@@ -307,16 +307,19 @@ public async Task DuplicateProjectIdSlnxAsync()
     }
 
     /// <summary>
-    /// Checks that an error is thrown if the solution contains an invalid project type id.
+    /// Verifies that a malformed project type id is loaded as an empty guid without errors, and
+    /// the solution is marked as tarnished.
     /// </summary>
     [Fact]
     public async Task InvalidProjectTypeSlnAsync()
     {
         ResourceStream invalidProjectType = SlnAssets.LoadResource("Invalid/InvalidProjectType.sln");
-        SolutionException ex = await Assert.ThrowsAsync<SolutionException>(
-            async () => _ = await SolutionSerializers.SlnFileV12.OpenAsync(invalidProjectType.Stream, CancellationToken.None));
-        Assert.StartsWith(Errors.InvalidProjectType, ex.Message);
-        Assert.Equal(5, ex.Line);
-        Assert.Null(ex.Column);
+        SolutionModel solution = await SolutionSerializers.SlnFileV12.OpenAsync(invalidProjectType.Stream, CancellationToken.None);
+        Assert.NotNull(solution.SerializerExtension);
+        Assert.True(solution.SerializerExtension.Tarnished);
+
+        SolutionProjectModel? project = solution.FindProject("InvalidProjectType.csproj");
+        Assert.NotNull(project);
+        Assert.Equal(Guid.Empty, project.TypeId);
     }
 }