diff --git a/src/multibody/geometry.hxx b/src/multibody/geometry.hxx
index 3bc9c1fdb2290134bae3d3ff9016872ed586cbb6..7048c943949bf9a67060b155cf34cf64efcfb178 100644
--- a/src/multibody/geometry.hxx
+++ b/src/multibody/geometry.hxx
@@ -213,6 +213,7 @@ namespace se3
     const Index & co1 = pair.first;     assert(co1<collisionObjects.size());
     const Index & co2 = pair.second;    assert(co2<collisionObjects.size());
 
+    collisionResult.clear();
     fcl::collide (&collisionObjects[co1],&collisionObjects[co2],
                   collisionRequest, collisionResult);