diff --git a/stack.sh b/stack.sh
index f47842b..c416a27 100755
--- a/stack.sh
+++ b/stack.sh
@@ -496,16 +496,18 @@ function exit_trap {
     # Kill the last spinner process
     kill_spinner
 
-    if [[ $r -ne 0 ]]; then
-        echo "Error on exit"
-        generate-subunit $DEVSTACK_START_TIME $SECONDS 'fail' >> ${SUBUNIT_OUTPUT}
-        if [[ -z $LOGDIR ]]; then
-            $TOP_DIR/tools/worlddump.py
-        else
-            $TOP_DIR/tools/worlddump.py -d $LOGDIR
-        fi
-    else
-        generate-subunit $DEVSTACK_START_TIME $SECONDS >> ${SUBUNIT_OUTPUT}
+    if $(which generate-subunit); then
+      if [[ $r -ne 0 ]]; then
+          echo "Error on exit"
+          generate-subunit $DEVSTACK_START_TIME $SECONDS 'fail' >> ${SUBUNIT_OUTPUT}
+          if [[ -z $LOGDIR ]]; then
+              $TOP_DIR/tools/worlddump.py
+          else
+              $TOP_DIR/tools/worlddump.py -d $LOGDIR
+          fi
+      else
+          generate-subunit $DEVSTACK_START_TIME $SECONDS >> ${SUBUNIT_OUTPUT}
+      fi
     fi
 
     exit $r