diff --git a/bilby/core/result.py b/bilby/core/result.py
index 076dbc88ccdee812ee124f8d826c23bf2e66bde2..ede6bf64327d1fa97745979ab3fb7b1def57c96f 100644
--- a/bilby/core/result.py
+++ b/bilby/core/result.py
@@ -1531,7 +1531,7 @@ def make_pp_plot(results, filename=None, save=True, confidence_interval=0.9,
     if title:
         ax.set_title("N={}, p-value={:2.4f}".format(
             len(results), pvals.combined_pvalue))
-    ax.set_xlabel("C.I")
+    ax.set_xlabel("C.I.")
     ax.set_ylabel("Fraction of events in C.I.")
     ax.legend(linewidth=1, labelspacing=0.25, fontsize=legend_fontsize)
     ax.set_xlim(0, 1)