diff --git a/packages/CLPBN/horus/Histogram.h b/packages/CLPBN/horus/Histogram.h
index 9b65f9f02..d60c2d22f 100644
--- a/packages/CLPBN/horus/Histogram.h
+++ b/packages/CLPBN/horus/Histogram.h
@@ -24,7 +24,7 @@ class HistogramSet
 
     void reset (void);
 
-    static vector<Histogram> getHistograms (unsigned ,unsigned);
+    static vector<Histogram> getHistograms (unsigned, unsigned);
 
     static unsigned nrHistograms (unsigned, unsigned);