diff --git a/src/CountMinSketch.hpp b/src/CountMinSketch.hpp
index ee8f619a3649f538348502dea8147994d678bd3f..22b2776fdc5592515cd6823987b2fd13905456bf 100644
--- a/src/CountMinSketch.hpp
+++ b/src/CountMinSketch.hpp
@@ -190,7 +190,7 @@ template<typename T> inline int CountMinSketch<T>::isRCovBelowThres(const readNu
             h=hash64to32(*it,j);
             min=cms_lambda_array[j] [h];
         }
-        (min<threshold)? a+=1: NULL;
+        (min<threshold)? a+=1:a;
         ++b;
     }
     return (2*a>b);