diff --git a/unittest/force-styles/tests/bond-mm3.yaml b/unittest/force-styles/tests/bond-mm3.yaml
index eb7443f1c2..f5ba5c237c 100644
--- a/unittest/force-styles/tests/bond-mm3.yaml
+++ b/unittest/force-styles/tests/bond-mm3.yaml
@@ -17,7 +17,9 @@ bond_coeff: ! |
   4 650.0 1.2
   5 450.0 1.0
 equilibrium: 5 1.5 1.1 1.3 1.2 1
-extract: ! ""
+extract: ! |
+  k2 1
+  r0 1
 natoms: 29
 init_energy: 4.247265008273143
 init_stress: ! |-