diff --git a/src/4_sommerfeld_model.md b/src/4_sommerfeld_model.md
index 3ccc0971890ad5b7c6c03d8fdb5288d9ffe8be48..5432712c1ae3728bdb3f2140b623ca7066cac5ca 100644
--- a/src/4_sommerfeld_model.md
+++ b/src/4_sommerfeld_model.md
@@ -44,7 +44,7 @@ Econt = kcont**2;
 
 fig = pyplot.figure();
 ax = fig.add_subplot(111);
-ax.plot(kcont, Econt, 'b-');
+ax.plot(kcont, Econt);
 ax.plot(ks, Edis, 'k.', markersize=10);
 for i in range(2*kf + 1):
     ax.plot([ks[i], ks[i]], [0.0, Edis[i]], 'k:');
@@ -133,9 +133,10 @@ Estates = kstates**2;
 
 fig = pyplot.figure();
 ax = fig.add_subplot(111);
+ax.fill_between(kfilled, Efilled, kf*kf);
 ax.plot([kf, kf], [0.0, kf*kf], 'k:');
 ax.plot(kstates, Estates, 'k--');
-ax.plot(kfilled, Efilled, 'b-', linewidth=4);
+ax.plot(kfilled, Efilled, linewidth=4);
 ax.axhline(kf*kf, linestyle="dotted", color='k');
 
 ax.set_xticks([kf]);