diff --git a/catmap/thermodynamics/enthalpy_entropy.py b/catmap/thermodynamics/enthalpy_entropy.py
index f61a8f3..ebc956f 100755
--- a/catmap/thermodynamics/enthalpy_entropy.py
+++ b/catmap/thermodynamics/enthalpy_entropy.py
@@ -1145,7 +1145,7 @@ def target(nu,kB_multiplier=kB_multiplier,T=T):
             SbykB = (get_entropy(nu,T)/kB)
             return (kB_multiplier - SbykB)**2
 
-        nu_cutoff = fmin_powell(target,10,disp=0)
+        nu_cutoff = fmin_powell(target,10,disp=0)[0] #nu_cutoff should be single-value
         return nu_cutoff
 
     def summary_text(self):