diff --git a/src/CLASS2/bond_class2.cpp b/src/CLASS2/bond_class2.cpp
index 8c5d8159bf..da1e8199e0 100644
--- a/src/CLASS2/bond_class2.cpp
+++ b/src/CLASS2/bond_class2.cpp
@@ -242,6 +242,9 @@ void BondClass2::born_matrix(int type, double rsq, int /*i*/, int /*j*/, double
 void *BondClass2::extract(const char *str, int &dim)
 {
   dim = 1;
+  if (strcmp(str, "k2") == 0) return (void *) k2;
+  if (strcmp(str, "k3") == 0) return (void *) k3;
+  if (strcmp(str, "k4") == 0) return (void *) k4;
   if (strcmp(str,"r0")==0) return (void*) r0;
   return nullptr;
 }