diff --git a/pypower/opf_costfcn.py b/pypower/opf_costfcn.py
index ab58406..823b274 100644
--- a/pypower/opf_costfcn.py
+++ b/pypower/opf_costfcn.py
@@ -102,7 +102,8 @@ def opf_costfcn(x, om, return_hessian=False):
 
     ## polynomial cost of P and Q
     df_dPgQg = zeros(2 * ng)        ## w.r.t p.u. Pg and Qg
-    df_dPgQg[ipol] = baseMVA * polycost(gencost[ipol, :], xx[ipol], 1)
+    if len(ipol):
+        df_dPgQg[ipol] = baseMVA * polycost(gencost[ipol, :], xx[ipol], 1)
     df = zeros(nxyz)
     df[iPg] = df_dPgQg[:ng]
     df[iQg] = df_dPgQg[ng:ng + ng]
diff --git a/pypower/opf_hessfcn.py b/pypower/opf_hessfcn.py
index de842f5..5177817 100644
--- a/pypower/opf_hessfcn.py
+++ b/pypower/opf_hessfcn.py
@@ -101,9 +101,10 @@ def opf_hessfcn(x, lmbda, om, Ybus, Yf, Yt, ppopt, il=None, cost_mult=1.0):
     d2f_dPg2 = zeros(ng)#sparse((ng, 1))               ## w.r.t. p.u. Pg
     d2f_dQg2 = zeros(ng)#sparse((ng, 1))               ## w.r.t. p.u. Qg
     ipolp = find(pcost[:, MODEL] == POLYNOMIAL)
-    d2f_dPg2[ipolp] = \
+    if len(ipol):
+        d2f_dPg2[ipolp] = \
             baseMVA**2 * polycost(pcost[ipolp, :], Pg[ipolp] * baseMVA, 2)
-    if any(qcost):          ## Qg is not free
+    if qcost.any():          ## Qg is not free
         ipolq = find(qcost[:, MODEL] == POLYNOMIAL)
         d2f_dQg2[ipolq] = \
                 baseMVA**2 * polycost(qcost[ipolq, :], Qg[ipolq] * baseMVA, 2)