diff --git a/mrdna/RELEASE-VERSION b/mrdna/RELEASE-VERSION
index f684ad2bc2e2abdfe0c6c56bf8cd5d5825d506f8..43fa3b489d8c21ab17ba349c8a289ac15c82ee18 100644
--- a/mrdna/RELEASE-VERSION
+++ b/mrdna/RELEASE-VERSION
@@ -1 +1 @@
-1.0a.dev67
+1.0a.dev69
diff --git a/mrdna/model/spring_from_lp.py b/mrdna/model/spring_from_lp.py
index b38012a005ec456b22aff5f6b81e4eafb0d53f7e..7cc237525423bb9cc1a6ce0b74c26f6cb5d08a8c 100644
--- a/mrdna/model/spring_from_lp.py
+++ b/mrdna/model/spring_from_lp.py
@@ -13,7 +13,7 @@ _integral = _integrate( lambda t: np.cos(t[np.newaxis,:])*np.sin(t[np.newaxis,:]
 assert( (np.diff(_integral) <= 0).sum() == 0 )
 def k_angle(sep,Lp):
     val = np.exp(-sep/Lp)
-    return interp(val,_integral,_k) * 0.00030461742 # convert to degree^2
+    return np.interp(val,_integral,_k) * 0.00030461742 # convert to degree^2
 
 """ Twist! """
 from scipy.special import erf
@@ -23,7 +23,7 @@ with np.errstate(divide='ignore',invalid='ignore'):
 def k_twist(sep,Lp,temperature=295):
     kT = temperature * 0.0019872065 # kcal/mol
     val = np.exp(-sep/Lp)
-    return interp(val,_integral_twist,_k_twist) * 2 * kT * 0.00030461742 # convert to degree^2
+    return np.interp(val,_integral_twist,_k_twist) * 2 * kT * 0.00030461742 # convert to degree^2
 
 def _TEST_get_spring_constant():