diff --git a/boost/boostcpp.jam b/boost/boostcpp.jam
index 257e70d..5afc6cc 100644
--- a/boost/boostcpp.jam
+++ b/boost/boostcpp.jam
@@ -136,7 +136,7 @@ rule tag ( name : type ? : property-set )
         else if $(layout) = system
         {
             result = [ common.format-name
-                <base>
+                <base> <threading>
                 -$(BUILD_ID)
                 : $(name) : $(type) : $(property-set) ] ;
         }
diff --git a/boost/tools/build/src/tools/common.jam b/boost/tools/build/src/tools/common.jam
index 8404feb..16a3fc7 100644
--- a/boost/tools/build/src/tools/common.jam
+++ b/boost/tools/build/src/tools/common.jam
@@ -907,7 +907,11 @@ local rule threading-tag ( name : type ? : property-set )
 {
     if <threading>multi in [ $(property-set).raw ]
     {
-        return mt ;
+        return ;
+    }
+    else
+    {
+        return st ;
     }
 }