diff --git a/src/quaternions.f90 b/src/quaternions.f90
index f5f5276e8..c337bd681 100644
--- a/src/quaternions.f90
+++ b/src/quaternions.f90
@@ -101,6 +101,8 @@ module quaternions
     assignment(=), &
     conjg, aimag, &
     log, exp, &
+    abs, dot_product, &
+    inverse, &
     real
 
 contains