diff --git a/Code/Mantid/Framework/API/src/AlgorithmHistory.cpp b/Code/Mantid/Framework/API/src/AlgorithmHistory.cpp
index 7815eb173458..88194356b66c 100644
--- a/Code/Mantid/Framework/API/src/AlgorithmHistory.cpp
+++ b/Code/Mantid/Framework/API/src/AlgorithmHistory.cpp
@@ -65,6 +65,8 @@ AlgorithmHistory::AlgorithmHistory(const std::string& name, int vers, const Kern
  */
 void AlgorithmHistory::setProperties(const Algorithm* const alg)
 {
+  //overwrite any existing properties
+  m_properties.clear();
   // Now go through the algorithm's properties and create the PropertyHistory objects.
   const std::vector<Property*>& properties = alg->getProperties();
   std::vector<Property*>::const_iterator it;