diff --git a/src/sdeventplus/internal/sdref.cpp b/src/sdeventplus/internal/sdref.cpp
index bbbbd3a..13720d1 100644
--- a/src/sdeventplus/internal/sdref.cpp
+++ b/src/sdeventplus/internal/sdref.cpp
@@ -8,7 +8,8 @@
 {
 
 template <typename T>
-SdRef<T>::SdRef(T* ref, Func take_ref, Func release_ref, SdEvent* sdevent) :
+SdRef<T>::SdRef(T* ref, Func take_ref, Func release_ref,
+                const SdEvent* sdevent) :
     SdRef(take_ref(sdevent, ref), take_ref, release_ref, std::false_type(),
           sdevent)
 {
@@ -16,7 +17,7 @@
 
 template <typename T>
 SdRef<T>::SdRef(T* ref, Func take_ref, Func release_ref, std::false_type,
-                SdEvent* sdevent) :
+                const SdEvent* sdevent) :
     sdevent(sdevent),
     take_ref(take_ref), release_ref(release_ref), ref(ref)
 {
diff --git a/src/sdeventplus/internal/sdref.hpp b/src/sdeventplus/internal/sdref.hpp
index 0b1395f..c0c77fc 100644
--- a/src/sdeventplus/internal/sdref.hpp
+++ b/src/sdeventplus/internal/sdref.hpp
@@ -13,12 +13,12 @@
 class SdRef
 {
   public:
-    using Func = std::function<T*(SdEvent*, T*)>;
+    using Func = std::function<T*(const SdEvent*, T*)>;
 
     SdRef(T* ref, Func take_ref, Func release_ref,
-          SdEvent* sdevent = &sdevent_impl);
+          const SdEvent* sdevent = &sdevent_impl);
     SdRef(T* ref, Func take_ref, Func release_ref, std::false_type,
-          SdEvent* sdevent = &sdevent_impl);
+          const SdEvent* sdevent = &sdevent_impl);
     virtual ~SdRef();
 
     SdRef(const SdRef& other);
@@ -29,7 +29,7 @@
     T* get() const;
 
   private:
-    SdEvent* sdevent;
+    const SdEvent* sdevent;
     Func take_ref;
     Func release_ref;
     T* ref;