diff --git a/toolbox/mm.cpp b/toolbox/mm.cpp
index f42e2f1..51ee9ed 100644
--- a/toolbox/mm.cpp
+++ b/toolbox/mm.cpp
@@ -1455,4 +1455,18 @@ namespace MM
 		return 0;
 	}
 
-}
\ No newline at end of file
+	uint16_t MaxApplZone(uint16_t trap)
+	{
+		// PROCEDURE MaxApplZone;
+
+		/*
+		 * on exit:
+		 * D0 Result code
+		 */
+
+		Log("%04x MaxApplZone\n", trap);
+
+		return 0;
+	}
+
+}
diff --git a/toolbox/mm.h b/toolbox/mm.h
index 3974c2d..2961e66 100644
--- a/toolbox/mm.h
+++ b/toolbox/mm.h
@@ -81,6 +81,8 @@ namespace MM
 	uint16_t HandleZone(uint16_t trap);
 	uint16_t GetZone(uint16_t trap);
 	uint16_t SetZone(uint16_t trap);
+
+	uint16_t MaxApplZone(uint16_t trap);
 }
 
 
diff --git a/toolbox/toolbox.cpp b/toolbox/toolbox.cpp
index d06b595..4a27847 100644
--- a/toolbox/toolbox.cpp
+++ b/toolbox/toolbox.cpp
@@ -254,6 +254,11 @@ namespace ToolBox {
 				d0 = MM::HandleZone(trap);
 				break;
 
+			// MaxApplZone
+			case 0xa063:
+				d0 = MM::MaxApplZone(trap);
+				break;
+
 			// ReadDateTime (VAR sees: LONGINT) : OSErr;
 			case 0xa039:
 				d0 = OS::ReadDateTime(trap);