diff --git a/src/unitvector.hh b/src/unitvector.hh
index 9c57d0be66c5ac2b78ac0afa102ecd1d5654d8e2..059d99daaa6db5d32591a20dfb210abb4fe6a5bd 100644
--- a/src/unitvector.hh
+++ b/src/unitvector.hh
@@ -128,6 +128,9 @@ public:
         result = A;
         result.axpy(-1*derivativeOfArcCosSquared(sp), B);
 
+        for (int i=0; i<dim; i++)
+            result[i] = b.projectOntoTangentSpace(result[i]);
+
         return result;
     }