diff --git a/src/ctobssim/ctobssim.cpp b/src/ctobssim/ctobssim.cpp
index 6a44f21..5cf4e33 100644
--- a/src/ctobssim/ctobssim.cpp
+++ b/src/ctobssim/ctobssim.cpp
@@ -559,6 +559,9 @@ void ctobssim::free_members(void)
  ***************************************************************************/
 void ctobssim::get_parameters(void)
 {
+    // Initialise seed vector
+    m_rans.clear();
+
     // If there are no observations in container then load them via user
     // parameters
     if (m_obs.size() == 0) {