--- tools/build/src/tools/darwin.jam.orig
+++ tools/build/src/tools/darwin.jam
@@ -431,6 +431,7 @@
     local support-ppc64 = 1 ;
     
     osx-version ?= $(.host-osx-version) ;
+    local osx-version-split = [ regex.split $(osx-version) \\. ] ;
 
     switch $(osx-version)
     {
@@ -440,7 +441,7 @@
         }
         
         case * :
-        if $(osx-version) && ! [ version.version-less [ regex.split $(osx-version) \\. ] : 10 6 ]
+        if $(osx-version) && ! [ version.version-less $(osx-version-split) : 10 6 ]
         {
             # When targeting 10.6:
             # - gcc 4.2 will give a compiler errir if ppc64 compilation is requested
@@ -452,7 +453,16 @@
     {
         case combined : 
         {
-            if $(address-model) = 32_64 {
+            if ! [ version.version-less $(osx-version-split) : 11 0 ]
+            {
+                # macOS 11.0 "Big Sur" and later is always 64-bit ...
+                if ( $(address_model) = 32 || $(address_model) = 32_64 ) {
+                    echo "'address_model' contains 32; macOS 11 or later builds 64 only; overriding" ;
+                    address-model = 64 ;
+                }
+                # ... and "combined" means Intel and ARM
+                options = -arch x86_64 -arch arm64 ;
+            } else if $(address-model) = 32_64 {
                 if $(support-ppc64) {
                     options = -arch i386 -arch ppc -arch x86_64 -arch ppc64 ;                    
                 } else {
@@ -500,8 +510,18 @@
         
         case arm :
         {
+            if ! [ version.version-less $(osx-version-split) : 11 0 ]
+            {
+                # macOS 11.0 "Big Sur" and later is always 64-bit
+                if ( $(address_model) = 32 || $(address_model) = 32_64 ) {
+                    echo "'address_model' contains 32; macOS 11 or later builds 64 only; overriding" ;
+                    address-model = 64 ;
+                }
+            }
             if $(instruction-set) {
                 options = -arch$(_)$(instruction-set) ;
+            } else if $(address-model) = 64 {
+                options = -arch arm64 ;
             } else {
                 options = -arch arm ;
             }