diff --git a/scripts/partial_tempering.sh b/scripts/partial_tempering.sh
index 199281f20b7f70bb10285c80c41c66ff0806880c..1fff2229a3f6e989dfcea92a888d05ab97c12eba 100755
--- a/scripts/partial_tempering.sh
+++ b/scripts/partial_tempering.sh
@@ -35,6 +35,9 @@ plumed partial_tempering \$scale < processed.top > topol\$i.top
 WARNING: It's not very robust and there might be force-field dependent issues!
 A few tests are strongly suggested.
 
+WARNING: This script only works if the `awk` command in your system corresponds to
+GNU awk. `mawk`, that is the default on Ubuntu 19, does not work correctly.
+
 1. Compare partial_tempering with scale=1.0 to non-scaled force field. E.g.
 grompp -o topol-unscaled.tpr
 grompp -pp