diff --git a/binarycpython/utils/population_extensions/slurm.py b/binarycpython/utils/population_extensions/slurm.py
index b19ed1c07a71a1eae8fae960c3976d364ca9591b..5dc8234b3d1931994fa7be1c43da41c826e47292 100644
--- a/binarycpython/utils/population_extensions/slurm.py
+++ b/binarycpython/utils/population_extensions/slurm.py
@@ -291,7 +291,7 @@ class slurm:
                 ]
                 + sys.argv[1:]
                 + [
-                    "start_at=" + str(jobarrayindex) + "-1",  # do we need the -1?
+                    "start_at=$((" + str(jobarrayindex) + "-1))",
                     "modulo=" + str(self.grid_options["slurm_njobs"]),
                     "slurm_njobs=" + str(self.grid_options["slurm_njobs"]),
                     "slurm_dir=" + self.grid_options["slurm_dir"],
diff --git a/install.sh b/install.sh
index f204a7922dcdba3ad27786cf0edd7ce43b1ac4a6..b9171547d5d648dbac19ef826961578c60e85de5 100755
--- a/install.sh
+++ b/install.sh
@@ -5,14 +5,14 @@ VERSION_NUMBER=$(cat "VERSION")
 echo "installing binarcpython version $VERSION_NUMBER"
 
 # Clean up all the stuff from before
-python setup.py clean --all
+python3 setup.py clean --all
 
 # Go into a directory that doesnt contain 'binarycpython' so pip will uninstall the one in the venv, not the local one.
 cd src
-pip uninstall -y binarycpython
+pip3 uninstall -y binarycpython
 cd ../
 
 # Create build, sdist and install it into the venv
-python setup.py build --force
-python setup.py sdist
-pip install -v dist/binarycpython-$VERSION_NUMBER.tar.gz
+python3 setup.py build --force
+python3 setup.py sdist
+pip3 install -v dist/binarycpython-$VERSION_NUMBER.tar.gz