diff --git a/build/Jamfile b/build/Jamfile
index 8c37ec6d..f14dc113 100644
--- a/build/Jamfile
+++ b/build/Jamfile
@@ -174,7 +174,7 @@ for local N in 2 3
     {
         alias $(lib_boost_python($(N))) ;
     }
-    if [ python.numpy ]
+    if $(py$(N)-version) && [ python.numpy ]
     {
         lib_boost_numpy $(py$(N)-version) ;
         libraries += $(lib_boost_numpy($(py$(N)-version))) ;