diff --git a/src/solver-op-space.cpp b/src/solver-op-space.cpp
index 0fd990876d6cf07f2febceeefa45532313074fa2..447480cf4d4a04948a0546044025d211bcf0e24c 100644
--- a/src/solver-op-space.cpp
+++ b/src/solver-op-space.cpp
@@ -647,7 +647,7 @@ namespace dynamicgraph
 	  {
 	    EIGEN_VECTOR_FROM_SIGNAL(qref,postureSIN(t));
 	    EIGEN_VECTOR_FROM_SIGNAL(q,positionSIN(t));
-	    const double Kp = Kv*Kv;
+	    const double Kp = .25*Kv*Kv;
 	    ref = (-Kp*(q-qref)-Kv*dq).tail(nbDofs);
 	  }
 	else