diff --git a/build/Jamfile.v2 b/build/Jamfile.v2
index faaf892..c07847a 100644
--- a/build/Jamfile.v2
+++ b/build/Jamfile.v2
@@ -79,7 +79,8 @@ local rule default_abi ( )
     local tmp = sysv ;
     if [ os.name ] = "NT" { tmp = ms ; }
     else if [ os.name ] = "CYGWIN" { tmp = ms ; }
-    else if [ os.platform ] in ARM ARM64 { tmp = aapcs ; }
+    else if [ os.platform ] = "ARM" { tmp = aapcs ; }
+    else if [ os.platform ] = "ARM64" { tmp = aapcs ; }
     else if [ os.platform ] = "MIPS32" { tmp = o32 ; }
     else if [ os.platform ] = "MIPS64" { tmp = n64 ; }
     return $(tmp) ;