diff --git a/src/setup/Units.cpp b/src/setup/Units.cpp
index 8087a85ca84c45a7eb190ba673ac109f0b74d2eb..2a1755d36df7877d806aaedad310a345d449d53a 100644
--- a/src/setup/Units.cpp
+++ b/src/setup/Units.cpp
@@ -148,6 +148,8 @@ Units::Units(const ActionOptions&ao):
     log.printf("  using physical units\n");
   }
   log.printf("  inside PLUMED, Boltzmann constant is %f\n",plumed.getAtoms().getKBoltzmann());
+
+  plumed.getAtoms().updateUnits();
 }
 
 }