diff --git a/unittest/force-styles/tests/improper-cvff.yaml b/unittest/force-styles/tests/improper-cvff.yaml
index 3a300de4d6..729768dc89 100644
--- a/unittest/force-styles/tests/improper-cvff.yaml
+++ b/unittest/force-styles/tests/improper-cvff.yaml
@@ -13,7 +13,10 @@ improper_style: cvff
 improper_coeff: ! |
   1  75.0 -1 5
   2  45.0 +1 2
-extract: ! ""
+extract: ! |
+  k 1
+  sign 1
+  multiplicity 1
 natoms: 29
 init_energy: 89.33266688553577
 init_stress: ! |2-