diff --git a/lib/scripts/isabelle-platform b/lib/scripts/isabelle-platform
--- a/lib/scripts/isabelle-platform
+++ b/lib/scripts/isabelle-platform
@@ -1,48 +1,41 @@
 # -*- shell-script -*- :mode=shellscript:
 #
 # determine general hardware and operating system type for Isabelle system tools
 #
 
 ISABELLE_PLATFORM_FAMILY=""
 ISABELLE_PLATFORM64=""
 ISABELLE_APPLE_PLATFORM64=""
 ISABELLE_WINDOWS_PLATFORM32=""
 ISABELLE_WINDOWS_PLATFORM64=""
 
 case $(uname -s) in
   Linux)
     ISABELLE_PLATFORM_FAMILY="linux"
     case $(uname -m) in
       aarch64)
         ISABELLE_PLATFORM64=arm64-linux
         ;;
       *)
         ISABELLE_PLATFORM64=x86_64-linux
         ;;
     esac
     ;;
   Darwin)
     ISABELLE_PLATFORM_FAMILY="macos"
-    case $(sw_vers -productVersion) in
-      10.10*|10.11*|10.12*|10.13*|10.14*)
-        ISABELLE_PLATFORM64=x86_64-darwin
+    ISABELLE_PLATFORM64=x86_64-darwin
+    case $(uname -a) in
+      *arm64*|*ARM64*)
+        ISABELLE_APPLE_PLATFORM64=arm64-darwin
         ;;
       *)
-        ISABELLE_PLATFORM64=x86_64-darwin
-        case $(uname -a) in
-          *arm64*|*ARM64*)
-            ISABELLE_APPLE_PLATFORM64=arm64-darwin
-            ;;
-          *)
-            ;;
-        esac
         ;;
     esac
     ;;
   CYGWIN_NT*)
     ISABELLE_PLATFORM_FAMILY="windows"
     ISABELLE_WINDOWS_PLATFORM32="x86-windows"
     ISABELLE_WINDOWS_PLATFORM64="x86_64-windows"
     ISABELLE_PLATFORM64=x86_64-cygwin
     ;;
 esac