diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2cfe6a2968..a584892cdd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,7 @@
 - Python: `app.saveProject`  and `app.saveProjectAs` now do project variable substitution, as in `app.saveProjectAs("[Variable]/output.ntp")`.
 - Fix ASCII curve import. #656
 - New color selection dialog for RGB and RGBA knobs. #210
+- Fix histogram smoothing (was 5 times too strong).
 
 ### Plugins
 
diff --git a/Engine/Smooth1D.cpp b/Engine/Smooth1D.cpp
index 2697cd9d0f..a83093bf69 100644
--- a/Engine/Smooth1D.cpp
+++ b/Engine/Smooth1D.cpp
@@ -171,15 +171,11 @@ NATRON_NAMESPACE_ANONYMOUS_EXIT
 namespace Smooth1D {
 
 
-    void iir_gaussianFilter1D(std::vector<float>& curve, int smoothingKernelSize)
+    void iir_gaussianFilter1D(std::vector<float>& curve, double sigma)
     {
         if (curve.size() < 3) {
             return;
         }
-        double sigma = 5.;
-        if (smoothingKernelSize > 1) {
-            sigma *= smoothingKernelSize;
-        }
 
         double filter[7];
         // calculate filter coefficients
diff --git a/Engine/Smooth1D.h b/Engine/Smooth1D.h
index 45ea3f4731..e6473287b6 100644
--- a/Engine/Smooth1D.h
+++ b/Engine/Smooth1D.h
@@ -33,7 +33,7 @@ NATRON_NAMESPACE_ENTER
 namespace Smooth1D
 {
 
-    void iir_gaussianFilter1D(std::vector<float>& curve, int smoothingKernelSize);
+    void iir_gaussianFilter1D(std::vector<float>& curve, double sigma);
 
     void laplacian_1D(std::vector<float>& curve);