diff --git a/tools/mmp/driver.cs b/tools/mmp/driver.cs
index 25d4b7106c14..9342d76afaba 100644
--- a/tools/mmp/driver.cs
+++ b/tools/mmp/driver.cs
@@ -807,12 +807,21 @@ static string GetRealPath (string path)
 
 		static string GetXamMacPrefix ()
 		{
-			var path = System.Reflection.Assembly.GetExecutingAssembly ().Location;
-
 			var envFrameworkPath = Environment.GetEnvironmentVariable ("XAMMAC_FRAMEWORK_PATH");
 			if (!String.IsNullOrEmpty (envFrameworkPath) && Directory.Exists (envFrameworkPath))
 				return envFrameworkPath;
 
+			var path = System.Reflection.Assembly.GetExecutingAssembly ().Location;
+
+#if DEBUG
+			var localPath = Path.GetDirectoryName (path);
+			while (localPath.Length > 1) {
+				if (Directory.Exists (Path.Combine (localPath, "_mac-build")))
+					return Path.Combine (localPath, "_mac-build", "Library", "Frameworks", "Xamarin.Mac.framework", "Versions", "Current");
+				localPath = Path.GetDirectoryName (localPath);
+			}
+#endif
+
 			path = GetRealPath (path);
 			return Path.GetDirectoryName (Path.GetDirectoryName (Path.GetDirectoryName (path)));
 		}
diff --git a/tools/mmp/mmp.csproj b/tools/mmp/mmp.csproj
index 42d45ea72440..600c5c7324c4 100644
--- a/tools/mmp/mmp.csproj
+++ b/tools/mmp/mmp.csproj
@@ -15,7 +15,7 @@
     <DebugType>full</DebugType>
     <Optimize>False</Optimize>
     <OutputPath>bin\Debug</OutputPath>
-    <DefineConstants>MONOMAC;MMP</DefineConstants>
+    <DefineConstants>MONOMAC;MMP;DEBUG</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <PlatformTarget>AnyCPU</PlatformTarget>