diff --git a/src/Cli/dotnet/commands/dotnet-sln/add/Program.cs b/src/Cli/dotnet/commands/dotnet-sln/add/Program.cs
index a7b2c0ec687d..0225d6cff89b 100644
--- a/src/Cli/dotnet/commands/dotnet-sln/add/Program.cs
+++ b/src/Cli/dotnet/commands/dotnet-sln/add/Program.cs
@@ -136,15 +136,16 @@ private void AddProject(SolutionModel solution, string solutionRelativeProjectPa
         {
             // Open project instance to see if it is a valid project
             ProjectRootElement projectRootElement = ProjectRootElement.Open(fullPath);
+            ProjectInstance projectInstance = new ProjectInstance(projectRootElement);
             SolutionProjectModel project;
             try
             {
                 project = solution.AddProject(solutionRelativeProjectPath, null, solutionFolder);
             }
-            catch (SolutionArgumentException ex) when (ex.ParamName == "projectTypeName")
+            catch (SolutionArgumentException ex) when (ex.Type == SolutionErrorType.InvalidProjectTypeReference)
             {
                 // If guid is not identified by vs-solutionpersistence, check in project element itself
-                var guid = projectRootElement.GetProjectTypeGuid();
+                var guid = projectRootElement.GetProjectTypeGuid() ?? projectInstance.GetDefaultProjectTypeGuid();
                 if (string.IsNullOrEmpty(guid))
                 {
                     Reporter.Error.WriteLine(CommonLocalizableStrings.UnsupportedProjectType, fullPath);
@@ -153,7 +154,6 @@ private void AddProject(SolutionModel solution, string solutionRelativeProjectPa
                 project = solution.AddProject(solutionRelativeProjectPath, guid, solutionFolder);
             }
             // Add settings based on existing project instance
-            ProjectInstance projectInstance = new ProjectInstance(projectRootElement);
             string projectInstanceId = projectInstance.GetProjectId();
             if (!string.IsNullOrEmpty(projectInstanceId) && serializer is ISolutionSerializer<SlnV12SerializerSettings>)
             {
diff --git a/test/TestAssets/TestProjects/TestAppWithEmptySln/App.slnx b/test/TestAssets/TestProjects/TestAppWithEmptySln/App.slnx
index 4e2253ddceed..ab94d1d554cc 100644
--- a/test/TestAssets/TestProjects/TestAppWithEmptySln/App.slnx
+++ b/test/TestAssets/TestProjects/TestAppWithEmptySln/App.slnx
@@ -1 +1 @@
-<Solution />
+<Solution />
\ No newline at end of file
diff --git a/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/App.sln b/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/App.sln
new file mode 100644
index 000000000000..8eca2536691f
--- /dev/null
+++ b/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/App.sln
@@ -0,0 +1,5 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.26006.2
+MinimumVisualStudioVersion = 10.0.40219.1
diff --git a/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/App.slnx b/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/App.slnx
new file mode 100644
index 000000000000..ab94d1d554cc
--- /dev/null
+++ b/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/App.slnx
@@ -0,0 +1 @@
+<Solution />
\ No newline at end of file
diff --git a/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/Unknown.unknownproj b/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/Unknown.unknownproj
new file mode 100644
index 000000000000..56d04f3da929
--- /dev/null
+++ b/test/TestAssets/TestProjects/TestAppWithSlnAndDefaultProjectType/Unknown.unknownproj
@@ -0,0 +1,7 @@
+<Project>
+
+  <PropertyGroup>
+    <DefaultProjectTypeGuid>{2F08BC15-189B-4804-B644-653F34C968A8}</DefaultProjectTypeGuid>
+  </PropertyGroup>
+
+</Project>
diff --git a/test/dotnet-sln.Tests/GivenDotnetSlnAdd.cs b/test/dotnet-sln.Tests/GivenDotnetSlnAdd.cs
index ebb82381c743..4c0ce7c32ec9 100644
--- a/test/dotnet-sln.Tests/GivenDotnetSlnAdd.cs
+++ b/test/dotnet-sln.Tests/GivenDotnetSlnAdd.cs
@@ -18,6 +18,7 @@ public static class ProjectTypeGuids
         public const string VBProjectTypeGuid = "{F184B08F-C81C-45F6-A57F-5ABD9991F28F}";
         public const string SolutionFolderGuid = "{2150E333-8FDC-42A3-9474-1A3956D46DE8}";
         public const string SharedProjectGuid = "{D954291E-2A0B-460D-934E-DC6B0785DB48}";
+        public const string DefaultProjectGuid = "{130159A9-F047-44B3-88CF-0CF7F02ED50F}";
     }
 
     public class GivenDotnetSlnAdd : SdkTest
@@ -749,13 +750,13 @@ public void WhenPassedAnUnknownProjectTypeItFails(string solutionCommand)
         [InlineData("sln", "SlnFileWithNoProjectReferencesAndCSharpProject", "CSharpProject", "CSharpProject.csproj", ProjectTypeGuids.CSharpProjectTypeGuid)]
         [InlineData("sln", "SlnFileWithNoProjectReferencesAndFSharpProject", "FSharpProject", "FSharpProject.fsproj", ProjectTypeGuids.FSharpProjectTypeGuid)]
         [InlineData("sln", "SlnFileWithNoProjectReferencesAndVBProject", "VBProject", "VBProject.vbproj", ProjectTypeGuids.VBProjectTypeGuid)]
-        [InlineData("sln", "SlnFileWithNoProjectReferencesAndUnknownProjectWithSingleProjectTypeGuid", "UnknownProject", "UnknownProject.unknownproj", "{130159A9-F047-44B3-88CF-0CF7F02ED50F}")]
-        [InlineData("sln", "SlnFileWithNoProjectReferencesAndUnknownProjectWithMultipleProjectTypeGuids", "UnknownProject", "UnknownProject.unknownproj", "{130159A9-F047-44B3-88CF-0CF7F02ED50F}")]
+        [InlineData("sln", "SlnFileWithNoProjectReferencesAndUnknownProjectWithSingleProjectTypeGuid", "UnknownProject", "UnknownProject.unknownproj", ProjectTypeGuids.DefaultProjectGuid)]
+        [InlineData("sln", "SlnFileWithNoProjectReferencesAndUnknownProjectWithMultipleProjectTypeGuids", "UnknownProject", "UnknownProject.unknownproj", ProjectTypeGuids.DefaultProjectGuid)]
         [InlineData("solution", "SlnFileWithNoProjectReferencesAndCSharpProject", "CSharpProject", "CSharpProject.csproj", ProjectTypeGuids.CSharpProjectTypeGuid)]
         [InlineData("solution", "SlnFileWithNoProjectReferencesAndFSharpProject", "FSharpProject", "FSharpProject.fsproj", ProjectTypeGuids.FSharpProjectTypeGuid)]
         [InlineData("solution", "SlnFileWithNoProjectReferencesAndVBProject", "VBProject", "VBProject.vbproj", ProjectTypeGuids.VBProjectTypeGuid)]
-        [InlineData("solution", "SlnFileWithNoProjectReferencesAndUnknownProjectWithSingleProjectTypeGuid", "UnknownProject", "UnknownProject.unknownproj", "{130159A9-F047-44B3-88CF-0CF7F02ED50F}")]
-        [InlineData("solution", "SlnFileWithNoProjectReferencesAndUnknownProjectWithMultipleProjectTypeGuids", "UnknownProject", "UnknownProject.unknownproj", "{130159A9-F047-44B3-88CF-0CF7F02ED50F}")]
+        [InlineData("solution", "SlnFileWithNoProjectReferencesAndUnknownProjectWithSingleProjectTypeGuid", "UnknownProject", "UnknownProject.unknownproj", ProjectTypeGuids.DefaultProjectGuid)]
+        [InlineData("solution", "SlnFileWithNoProjectReferencesAndUnknownProjectWithMultipleProjectTypeGuids", "UnknownProject", "UnknownProject.unknownproj", ProjectTypeGuids.DefaultProjectGuid)]
         public async Task WhenPassedAProjectItAddsCorrectProjectTypeGuid(
             string solutionCommand,
             string testAsset,
@@ -788,7 +789,7 @@ public async Task WhenPassedAProjectItAddsCorrectProjectTypeGuid(
         [InlineData("solution", ".sln")]
         [InlineData("sln", ".slnx")]
         [InlineData("solution", ".slnx")]
-        public void WhenPassedAProjectWithoutATypeGuidItErrors(string solutionCommand, string solutionExtension)
+        public void WhenPassedAProjectWithoutATypeGuidNorDefaultTypeGuidItErrors(string solutionCommand, string solutionExtension)
         {
             var solutionDirectory = _testAssetsManager
                 .CopyTestAsset("SlnFileWithNoProjectReferencesAndUnknownProjectType", identifier: $"GivenDotnetSlnAdd-{solutionCommand}{solutionExtension}")
@@ -814,6 +815,26 @@ public void WhenPassedAProjectWithoutATypeGuidItErrors(string solutionCommand, s
                 .BeVisuallyEquivalentTo(contentBefore);
         }
 
+        [Theory]
+        [InlineData("sln", ".sln")]
+        [InlineData("solution", ".sln")]
+        [InlineData("sln", ".slnx")]
+        [InlineData("solution", ".slnx")]
+        public void WhenPassedAProjectWithDefaultProjectGuidItPasses(string solutionCommand, string solutionExtension)
+        {
+            var solutionDirectory = _testAssetsManager
+                .CopyTestAsset("TestAppWithSlnAndDefaultProjectType", identifier: $"GivenDotnetSlnAdd-{solutionCommand}{solutionExtension}")
+                .WithSource()
+                .Path;
+            
+            var cmd = new DotnetCommand(Log)
+                .WithWorkingDirectory(solutionDirectory)
+                .Execute(solutionCommand, $"App{solutionExtension}", "add", "Unknown.unknownproj");
+            
+            cmd.Should().Pass();
+            cmd.StdErr.Should().BeEmpty();
+        }
+
         [Theory]
         [InlineData("sln", ".sln")]
         [InlineData("solution", ".sln")]