diff --git a/include/pinocchio/multibody/joint/joint-mimic.hpp b/include/pinocchio/multibody/joint/joint-mimic.hpp
index 53aeaa25c..da977040e 100644
--- a/include/pinocchio/multibody/joint/joint-mimic.hpp
+++ b/include/pinocchio/multibody/joint/joint-mimic.hpp
@@ -168,7 +168,7 @@ namespace pinocchio
     struct TransposeConst
     {
       const ScaledJointMotionSubspaceTpl & ref;
-      TransposeConst(const ScaledJointMotionSubspaceTpl & ref)
+      explicit TransposeConst(const ScaledJointMotionSubspaceTpl & ref)
       : ref(ref)
       {
       }
diff --git a/include/pinocchio/serialization/joints-model.hpp b/include/pinocchio/serialization/joints-model.hpp
index 485558752..45fec54d5 100644
--- a/include/pinocchio/serialization/joints-model.hpp
+++ b/include/pinocchio/serialization/joints-model.hpp
@@ -71,7 +71,7 @@ namespace boost
       Derived & joint;
 
     public:
-      SetJointIndexes(Derived & joint)
+      explicit SetJointIndexes(Derived & joint)
       : joint(joint) {};
 
       void run(pinocchio::JointIndex i_id, int i_q, int i_v, int i_j)
@@ -86,7 +86,8 @@ namespace boost
       pinocchio::JointModelMimicTpl<Scalar, Options, JointCollectionTpl> & joint;
 
     public:
-      SetJointIndexes(pinocchio::JointModelMimicTpl<Scalar, Options, JointCollectionTpl> & joint)
+      explicit SetJointIndexes(
+        pinocchio::JointModelMimicTpl<Scalar, Options, JointCollectionTpl> & joint)
       : joint(joint) {};
 
       void run(pinocchio::JointIndex i_id, int i_q, int i_v, int i_j)