diff --git a/docs/website/mtouch-errors.md b/docs/website/mtouch-errors.md
index 2faa3f52b208..9d0b913dc072 100644
--- a/docs/website/mtouch-errors.md
+++ b/docs/website/mtouch-errors.md
@@ -966,6 +966,18 @@ This warning is shown if the assemblies names given to the `--interpreter` optio
 
 <!-- 0143-0144: used by mmp -->
 
+<a name="MT0145" />
+
+### MT0145: Please use device builds on WatchOS.
+
+This error occurs if you use combined device builds for a Watch extension project. Per device builds are default in new projects.
+
+<a name="MT0146" />
+
+### MT0146: ARM64_32 Debug mode requires --interpreter[=all], forcing it.
+
+This warning is shown when `--interpreter` isn't specified explicitly for ARM64_32 Debug builds. The AOT compiler can't be used because it doesn't support ARM64_32.
+
 # MT1xxx: Project related error messages
 
 ### MT10xx: Installer / mtouch
diff --git a/tools/mtouch/mtouch.cs b/tools/mtouch/mtouch.cs
index 74e8afcabd51..b53ea6463b66 100644
--- a/tools/mtouch/mtouch.cs
+++ b/tools/mtouch/mtouch.cs
@@ -1353,11 +1353,11 @@ static int Main2 (string[] args)
 				// interpreter can use some extra code (e.g. SRE) that is not shipped in the default (AOT) profile
 				app.EnableRepl = true;
 			} else {
-				if (app.Platform == ApplePlatform.WatchOS && app.IsArchEnabled (Abi.ARM64_32)) {
+				if (app.Platform == ApplePlatform.WatchOS && app.IsArchEnabled (Abi.ARM64_32) && app.BitCodeMode != BitCodeMode.LLVMOnly) {
 					if (app.IsArchEnabled (Abi.ARMv7k)) {
-						throw ErrorHelper.CreateError (99, "Please use device builds on WatchOS.");
+						throw ErrorHelper.CreateError (145, "Please use device builds on WatchOS.");
 					} else {
-						ErrorHelper.Warning (99, "ARM64_32 Debug mode requires --interpreter[=all], forcing it.");
+						ErrorHelper.Warning (146, "ARM64_32 Debug mode requires --interpreter[=all], forcing it.");
 						app.UseInterpreter = true;
 						app.InterpretedAssemblies.Clear ();
 					}