diff -up ./gazebo/sensors/GaussianNoiseModel.cc.gaussianstddev ./gazebo/sensors/GaussianNoiseModel.cc

--- ./gazebo/sensors/GaussianNoiseModel.cc.gaussianstddev	2020-01-18 13:54:05.637290373 -0500

+++ ./gazebo/sensors/GaussianNoiseModel.cc	2020-01-18 13:55:36.961532289 -0500

@@ -193,8 +193,12 @@ double GaussianNoiseModel::GetBias() con

 //////////////////////////////////////////////////

 void GaussianNoiseModel::SampleBias()

 {

-  this->bias =

+  if (this->biasStdDev > 0) {

+    this->bias =

       ignition::math::Rand::DblNormal(this->biasMean, this->biasStdDev);

+  } else {

+    this->bias = this->biasMean;

+  }

   // With equal probability, we pick a negative bias (by convention,

   // rateBiasMean should be positive, though it would work fine if

   // negative).