diff --git a/unittest/force-styles/tests/improper-class2.yaml b/unittest/force-styles/tests/improper-class2.yaml
index d60ae48602..eba334a1e6 100644
--- a/unittest/force-styles/tests/improper-class2.yaml
+++ b/unittest/force-styles/tests/improper-class2.yaml
@@ -15,7 +15,7 @@ improper_coeff: ! |
   2  45.0  10
   *  aa 75 42 31 125.4 130.01 115.06
 extract: ! |
-  k0 1
+  k 1
   chi0 1
 natoms: 29
 init_energy: 1375.7372366975192