diff --git a/src/dr/evomodel/bigfasttree/thorney/BranchLengthLikelihoodDelegate.java b/src/dr/evomodel/bigfasttree/thorney/BranchLengthLikelihoodDelegate.java
index 1c3d72a948..311bb91fc5 100644
--- a/src/dr/evomodel/bigfasttree/thorney/BranchLengthLikelihoodDelegate.java
+++ b/src/dr/evomodel/bigfasttree/thorney/BranchLengthLikelihoodDelegate.java
@@ -4,5 +4,5 @@
 public interface BranchLengthLikelihoodDelegate  {
      double getLogLikelihood(double mutations, double branchLength);
 
-     double getGradientWrtTime(double mutations, double time);
+     public double getGradientWrtTime(double mutations, double time, double branchRate);
 }
\ No newline at end of file
diff --git a/src/dr/evomodel/bigfasttree/thorney/PoissonBranchLengthLikelihoodDelegate.java b/src/dr/evomodel/bigfasttree/thorney/PoissonBranchLengthLikelihoodDelegate.java
index b82ce93eaf..b898d2d17b 100644
--- a/src/dr/evomodel/bigfasttree/thorney/PoissonBranchLengthLikelihoodDelegate.java
+++ b/src/dr/evomodel/bigfasttree/thorney/PoissonBranchLengthLikelihoodDelegate.java
@@ -21,13 +21,12 @@ public double getLogLikelihood(double mutations, double branchLength) {
 
 
     @Override
-    public double getGradientWrtTime(double mutations, double branchLength) { // TODO: better chain rule handling
+    public double getGradientWrtTime(double mutations, double time, double branchRate) { // TODO: better chain rule handling
         // if (!(this.branchRateModel instanceof StrictClockBranchRates)){
         //     throw new RuntimeException("gradients are only implemented for a strict clock model");
         // }
         // double rate = (double) branchRateModel.getVariable(0).getValue(0);
-        // return SaddlePointExpansion.logPoissonMeanDerivative(time * rate * scale, (int) Math.round(mutations)) * rate * scale;
-        throw new RuntimeException("gradients are not implemented for this model");
+        return SaddlePointExpansion.logPoissonMeanDerivative(time * branchRate * scale, (int) Math.round(mutations)) * branchRate * scale;
     }
 
 
diff --git a/src/dr/evomodel/bigfasttree/thorney/ThorneyTreeGradient.java b/src/dr/evomodel/bigfasttree/thorney/ThorneyTreeGradient.java
index 4f2cb07490..0c7ef0d073 100644
--- a/src/dr/evomodel/bigfasttree/thorney/ThorneyTreeGradient.java
+++ b/src/dr/evomodel/bigfasttree/thorney/ThorneyTreeGradient.java
@@ -26,7 +26,7 @@
 package dr.evomodel.bigfasttree.thorney;
 
 import dr.evolution.tree.NodeRef;
-import dr.evolution.tree.Tree;
+import dr.evomodel.branchratemodel.BranchRateModel;
 import dr.evomodel.tree.TreeModel;
 import dr.evomodel.tree.TreeParameterModel;
 import dr.evomodel.treedatalikelihood.TreeDataLikelihood;
@@ -48,7 +48,7 @@ public class ThorneyTreeGradient implements GradientWrtParameterProvider, Report
     private final TreeParameterModel indexHelper;
     private final double[] branchGradient;
     private final ThorneyDataLikelihoodDelegate dataLikelihoodDelegate;
-
+    private final BranchRateModel branchRateModel;
     public ThorneyTreeGradient(TreeDataLikelihood likelihood) {
         this.likelihood = likelihood;
         this.tree = (TreeModel)likelihood.getTree();
@@ -56,6 +56,7 @@ public ThorneyTreeGradient(TreeDataLikelihood likelihood) {
         this.nodeHeightProxyParameter = new NodeHeightProxyParameter("ThorneyTreeGradient.NodeHeightProxyParameter", this.tree, true);
         this.branchGradient = new double[tree.getNodeCount() - 1];
         this.indexHelper = new TreeParameterModel(tree, new Parameter.Default(branchGradient), false);
+        this.branchRateModel = likelihood.getBranchRateModel();
 
 
     }
@@ -80,7 +81,8 @@ private void calculateBranchGradient() {
             NodeRef node = tree.getNode(indexHelper.getNodeNumberFromParameterIndex(i));
             double time = tree.getBranchLength(node);
             double mutations = dataLikelihoodDelegate.getMutationMap().getMutations(node);
-            branchGradient[i] = dataLikelihoodDelegate.getBranchLengthLikelihoodDelegate().getGradientWrtTime(mutations, time);
+            double rate = branchRateModel.getBranchRate(tree,node);
+            branchGradient[i] = dataLikelihoodDelegate.getBranchLengthLikelihoodDelegate().getGradientWrtTime(mutations, time, rate);
         }
     }