diff --git a/partitioned-heat-conduction/fenics/run.sh b/partitioned-heat-conduction/fenics/run.sh
index e31f07a10..e51fb750b 100755
--- a/partitioned-heat-conduction/fenics/run.sh
+++ b/partitioned-heat-conduction/fenics/run.sh
@@ -1,6 +1,14 @@
 #!/bin/sh
 set -e -u
 
+usage() { echo "Usage: cmd [-d] [-n]" 1>&2; exit 1; }
+
+# Check if no input argument was provided
+if [ -z "$*" ] ; then
+	usage
+fi
+
+# Select appropriate case
 while getopts ":dn" opt; do
   case ${opt} in
   d)
@@ -9,8 +17,8 @@ while getopts ":dn" opt; do
   n)
     python3 heat.py -n --error-tol 10e-3
     ;;
-  \?)
-    echo "Usage: cmd [-d] [-n]"
+  *)
+    usage
     ;;
   esac
 done
diff --git a/partitioned-heat-conduction/nutils/run.sh b/partitioned-heat-conduction/nutils/run.sh
index 43e97b70f..b3048a04f 100755
--- a/partitioned-heat-conduction/nutils/run.sh
+++ b/partitioned-heat-conduction/nutils/run.sh
@@ -1,6 +1,13 @@
 #!/bin/sh
 set -e -u
 
+usage() { echo "Usage: cmd [-d] [-n]" 1>&2; exit 1; }
+
+# Check if no input argument was provided
+if [ -z "$*" ] ; then
+        usage
+fi
+
 while getopts ":dn" opt; do
   case ${opt} in
   d)
@@ -11,8 +18,8 @@ while getopts ":dn" opt; do
     rm -rf Neumann-*.vtk
     python3 heat.py --side=Neumann
     ;;
-  \?)
-    echo "Usage: cmd [-d] [-n]"
+  *)
+    usage
     ;;
   esac
 done