diff --git a/Xamarin.MacDev/MacCatalystSupport.cs b/Xamarin.MacDev/MacCatalystSupport.cs
new file mode 100644
index 0000000..07934b8
--- /dev/null
+++ b/Xamarin.MacDev/MacCatalystSupport.cs
@@ -0,0 +1,93 @@
+//
+// MacCatalystSupport.cs
+//
+// Author: Rolf Kvinge <rolf@xamarin.com>
+//
+// Copyright (c) 2021 Microsoft Corp.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Xamarin.MacDev {
+	public static class MacCatalystSupport {
+		// Versions for Mac Catalyst are complicated. In some cases we have to use the
+		// corresponding iOS version of the SDK, and in some cases we have to use the
+		// macOS version that iOS version correspond to. In Xcode, when you select the
+		// deployment target, you select a macOS version in the UI, but the corresponding
+		// iOS version is written to the project file. This means that there's a mapping
+		// between the two, and it turns out Apple stores it in the SDKSettings.plist in
+		// the macOS SDK. Here we provide a method that loads Apple's mapping from the
+		// SDKSettings.plist.
+		public static void LoadVersionMaps (string sdkDirectory, out Dictionary<string, string> map_ios_to_macos, out Dictionary<string, string> map_macos_to_ios)
+		{
+			map_ios_to_macos = new Dictionary<string, string> ();
+			map_macos_to_ios = new Dictionary<string, string> ();
+
+			var fn = Path.Combine (sdkDirectory, "SDKSettings.plist");
+			var plist = PDictionary.FromFile (fn);
+			if (plist.TryGetValue ("VersionMap", out PDictionary versionMap)) {
+				if (versionMap.TryGetValue ("iOSMac_macOS", out PDictionary versionMapiOSToMac)) {
+					foreach (var kvp in versionMapiOSToMac)
+						map_ios_to_macos [kvp.Key] = ((PString) kvp.Value).Value;
+				}
+				if (versionMap.TryGetValue ("macOS_iOSMac", out PDictionary versionMapMacToiOS)) {
+					foreach (var kvp in versionMapMacToiOS)
+						map_macos_to_ios [kvp.Key] = ((PString) kvp.Value).Value;
+				}
+			}
+		}
+
+		public static bool TryGetMacOSVersion (string sdkDirectory, Version iOSVersion, out Version macOSVersion)
+		{
+			macOSVersion = null;
+
+			if (!TryGetMacOSVersion (sdkDirectory, iOSVersion.ToString (), out var strValue))
+				return false;
+
+			return Version.TryParse (strValue, out macOSVersion);
+		}
+
+		public static bool TryGetMacOSVersion (string sdkDirectory, string iOSVersion, out string macOSVersion)
+		{
+			LoadVersionMaps (sdkDirectory, out var map, out var _);
+
+			return map.TryGetValue (iOSVersion.ToString (), out macOSVersion);
+		}
+
+		public static bool TryGetiOSVersion (string sdkDirectory, Version macOSVersion, out Version iOSVersion)
+		{
+			iOSVersion = null;
+
+			if (!TryGetiOSVersion (sdkDirectory, macOSVersion.ToString (), out var strValue))
+				return false;
+
+			return Version.TryParse (strValue, out iOSVersion);
+		}
+
+		public static bool TryGetiOSVersion (string sdkDirectory, string macOSVersion, out string iOSVersion)
+		{
+			LoadVersionMaps (sdkDirectory, out var _, out var map);
+
+			return map.TryGetValue (macOSVersion.ToString (), out iOSVersion);
+		}
+	}
+}
diff --git a/Xamarin.MacDev/MacOSXSdk.cs b/Xamarin.MacDev/MacOSXSdk.cs
index 4f04044..d22c077 100644
--- a/Xamarin.MacDev/MacOSXSdk.cs
+++ b/Xamarin.MacDev/MacOSXSdk.cs
@@ -167,21 +167,7 @@ void LoadCatalystVersionMaps (string version)
 			if (catalyst_version_map_ios_to_macos != null && catalyst_version_map_macos_to_ios != null)
 				return;
 
-			catalyst_version_map_ios_to_macos = new Dictionary<string, string> ();
-			catalyst_version_map_macos_to_ios = new Dictionary<string, string> ();
-
-			var fn = GetSdkPlistFilename (version);
-			var plist = PDictionary.FromFile (fn);
-			if (plist.TryGetValue ("VersionMap", out PDictionary versionMap)) {
-				if (versionMap.TryGetValue ("iOSMac_macOS", out PDictionary versionMapiOSToMac)) {
-					foreach (var kvp in versionMapiOSToMac)
-						catalyst_version_map_ios_to_macos [kvp.Key] = ((PString) kvp.Value).Value;
-				}
-				if (versionMap.TryGetValue ("macOS_iOSMac", out PDictionary versionMapMacToiOS)) {
-					foreach (var kvp in versionMapMacToiOS)
-						catalyst_version_map_macos_to_ios [kvp.Key] = ((PString) kvp.Value).Value;
-				}
-			}
+			MacCatalystSupport.LoadVersionMaps (GetSdkPath (version), out catalyst_version_map_ios_to_macos, out catalyst_version_map_macos_to_ios);
 		}
 
 		public Dictionary<string, string> GetCatalystVersionMap_iOS_to_Mac (string version)