diff --git a/Code/Mantid/Framework/SINQ/inc/MantidSINQ/PoldiUtilities/Poldi2DFunction.h b/Code/Mantid/Framework/SINQ/inc/MantidSINQ/PoldiUtilities/Poldi2DFunction.h
index 3c5b9dc6ed4c..f96edb10ad38 100644
--- a/Code/Mantid/Framework/SINQ/inc/MantidSINQ/PoldiUtilities/Poldi2DFunction.h
+++ b/Code/Mantid/Framework/SINQ/inc/MantidSINQ/PoldiUtilities/Poldi2DFunction.h
@@ -50,6 +50,10 @@ class MANTID_SINQ_DLL Poldi2DFunction : virtual public API::IFunction1DSpectrum,
     virtual void functionDeriv(const API::FunctionDomain &domain, API::Jacobian &jacobian);
     
     virtual void function1DSpectrum(const API::FunctionDomain1DSpectrum &domain, API::FunctionValues &values) const;
+
+    void iterationFinished();
+private:
+    size_t m_iteration;
 };
 
 
diff --git a/Code/Mantid/Framework/SINQ/src/PoldiUtilities/Poldi2DFunction.cpp b/Code/Mantid/Framework/SINQ/src/PoldiUtilities/Poldi2DFunction.cpp
index 265de7da6055..eb9f1e765ee1 100644
--- a/Code/Mantid/Framework/SINQ/src/PoldiUtilities/Poldi2DFunction.cpp
+++ b/Code/Mantid/Framework/SINQ/src/PoldiUtilities/Poldi2DFunction.cpp
@@ -8,7 +8,8 @@ using namespace API;
 
 Poldi2DFunction::Poldi2DFunction() :
     IFunction1DSpectrum(),
-    CompositeFunction()
+    CompositeFunction(),
+    m_iteration(0)
 {
 }
 
@@ -24,6 +25,12 @@ Poldi2DFunction::Poldi2DFunction() :
 void Poldi2DFunction::function(const FunctionDomain &domain, FunctionValues &values) const
 {
     CompositeFunction::function(domain, values);
+
+    if(m_iteration > 0) {
+        for(size_t i = 0; i < values.size(); ++i) {
+            values.setFitWeight(i, 1.0/sqrt(values.getCalculated(i) + 0.1));
+        }
+    }
 }
 
 /**
@@ -50,6 +57,11 @@ void Poldi2DFunction::function1DSpectrum(const FunctionDomain1DSpectrum &domain,
     UNUSED_ARG(values);
 }
 
+void Poldi2DFunction::iterationFinished()
+{
+    ++m_iteration;
+}
+
 
 
 } // namespace Poldi
diff --git a/Code/Mantid/Framework/SINQ/test/Poldi2DFunctionTest.h b/Code/Mantid/Framework/SINQ/test/Poldi2DFunctionTest.h
index 4c7275c5c479..dfa5170163dc 100644
--- a/Code/Mantid/Framework/SINQ/test/Poldi2DFunctionTest.h
+++ b/Code/Mantid/Framework/SINQ/test/Poldi2DFunctionTest.h
@@ -56,6 +56,39 @@ class Poldi2DFunctionTest : public CxxTest::TestSuite
         TS_ASSERT_EQUALS(values[9], 2.0);
     }
 
+    void testIterationBehavior()
+    {
+        boost::shared_ptr<Poldi2DFunction> function2D(new Poldi2DFunction);
+
+        IFunction_sptr first(new SummingFunction);
+        IFunction_sptr second(new SummingFunction);
+
+        function2D->addFunction(first);
+        function2D->addFunction(second);
+
+        // x doesn't matter for that function
+        std::vector<double> x(10, 1.0);
+
+        FunctionDomain1DSpectrum domain(0, x);
+        FunctionValues values(domain);
+
+
+        function2D->function(domain, values);
+
+        for(size_t i = 0; i < values.size(); ++i) {
+            TS_ASSERT_THROWS(values.getFitWeight(i), std::runtime_error);
+        }
+
+        function2D->iterationFinished();
+
+        function2D->function(domain, values);
+
+        for(size_t i = 0; i < values.size(); ++i) {
+            TS_ASSERT_THROWS_NOTHING(values.getFitWeight(i));
+            TS_ASSERT_EQUALS(values.getFitWeight(i), 1.0/sqrt(fabs(values.getCalculated(i) + 0.1)));
+        }
+    }
+
 private:
     /* small test function that behaves like PoldiSpectrumDomainFunction
      * in that it uses FunctionValues::addToCalculated.