diff --git a/runtime/base/histogram.h b/runtime/base/histogram.h
index d4eb1f4..4e5d29a 100644
--- a/runtime/base/histogram.h
+++ b/runtime/base/histogram.h
@@ -49,7 +49,7 @@
   // cumulative_freq[i] = sum(frequency[j] : 0 < j < i )
   // Accumulative summation of percentiles; which is the frequency / SampleSize
   // cumulative_perc[i] = sum(frequency[j] / SampleSize : 0 < j < i )
-  void CreateHistogram(CumulativeData* data);
+  void CreateHistogram(CumulativeData* data) const;
   // Reset the cumulative values, next time CreateHistogram is called it will recreate the cache.
   void Reset();
   double Mean() const;