diff --git a/inst/include/cpp11/sexp.hpp b/inst/include/cpp11/sexp.hpp
index 1517c5af..9f6f5e18 100644
--- a/inst/include/cpp11/sexp.hpp
+++ b/inst/include/cpp11/sexp.hpp
@@ -20,14 +20,15 @@ class sexp {
   sexp() = default;
 
   sexp(SEXP data) : data_(data), preserve_token_(preserved.insert(data_)) {
-    // REprintf("created %x %x : %i\n", data_, preserve_token_, protect_head_size());
+    // REprintf("created %p %p\n", reinterpret_cast<void*>(data_),
+    //          reinterpret_cast<void*>(preserve_token_));
   }
 
   sexp(const sexp& rhs) {
     data_ = rhs.data_;
     preserve_token_ = preserved.insert(data_);
-    // REprintf("copied %x new protect %x : %i\n", rhs.data_, preserve_token_,
-    // protect_head_size());
+    // REprintf("copied %p new protect %p\n", reinterpret_cast<void*>(rhs.data_),
+    //          reinterpret_cast<void*>(preserve_token_));
   }
 
   sexp(sexp&& rhs) {
@@ -37,7 +38,7 @@ class sexp {
     rhs.data_ = R_NilValue;
     rhs.preserve_token_ = R_NilValue;
 
-    // REprintf("moved %x : %i\n", rhs.data_, protect_head_size());
+    // REprintf("moved %p\n", reinterpret_cast<void*>(rhs.data_));
   }
 
   sexp& operator=(const sexp& rhs) {
@@ -45,7 +46,7 @@ class sexp {
 
     data_ = rhs.data_;
     preserve_token_ = preserved.insert(data_);
-    // REprintf("assigned %x : %i\n", rhs.data_, protect_head_size());
+    // REprintf("assigned %p\n", reinterpret_cast<void*>(rhs.data_));
     return *this;
   }