diff --git a/src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs b/src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs
index 318870b924..ef1f8a2919 100644
--- a/src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs
+++ b/src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs
@@ -332,7 +332,10 @@ namespace ICSharpCode.SharpDevelop.Project
 				Dictionary<string, string> globalProps = new Dictionary<string, string>();
 				globalProps["Configuration"] = configuration;
 				globalProps["Platform"] = platform;
-				var project = new MSBuild.Project(projectFile, globalProps, projectFile.ToolsVersion, projectCollection);
+				string toolsVersion = projectFile.ToolsVersion;
+				if (string.IsNullOrEmpty(toolsVersion))
+					toolsVersion = projectCollection.DefaultToolsVersion;
+				var project = new MSBuild.Project(projectFile, globalProps, toolsVersion, projectCollection);
 				return new ConfiguredProject(this, project);
 			} catch {
 				// Leave lock only on exceptions.
diff --git a/src/Main/Base/Project/Src/Project/MSBuildEngine.cs b/src/Main/Base/Project/Src/Project/MSBuildEngine.cs
index 916a667194..0ddf8a8f6b 100644
--- a/src/Main/Base/Project/Src/Project/MSBuildEngine.cs
+++ b/src/Main/Base/Project/Src/Project/MSBuildEngine.cs
@@ -76,7 +76,7 @@ namespace ICSharpCode.SharpDevelop.Project
 		}
 		
 		
-		public static void StartBuild(MSBuildBasedProject project, ProjectBuildOptions options, IBuildFeedbackSink feedbackSink, IEnumerable<string> additionalTargetFiles)
+		public static void StartBuild(IProject project, ProjectBuildOptions options, IBuildFeedbackSink feedbackSink, IEnumerable<string> additionalTargetFiles)
 		{
 			if (project == null)
 				throw new ArgumentNullException("project");
@@ -92,12 +92,12 @@ namespace ICSharpCode.SharpDevelop.Project
 			engine.StartBuild();
 		}
 		
-		MSBuildBasedProject project;
+		IProject project;
 		ProjectBuildOptions options;
 		IBuildFeedbackSink feedbackSink;
 		IEnumerable<string> additionalTargetFiles;
 		
-		private MSBuildEngine(MSBuildBasedProject project, ProjectBuildOptions options, IBuildFeedbackSink feedbackSink)
+		private MSBuildEngine(IProject project, ProjectBuildOptions options, IBuildFeedbackSink feedbackSink)
 		{
 			this.project = project;
 			this.options = options;