diff --git a/src/object/sp-clippath.cpp b/src/object/sp-clippath.cpp
index 0b1b1bafa73b3629542494265b5bf984765e6ebe..2b86edc41db7a28998b32c5e955f3bb7927ac179 100644
--- a/src/object/sp-clippath.cpp
+++ b/src/object/sp-clippath.cpp
@@ -308,10 +308,9 @@ bool SPClipPathReference::_acceptObject(SPObject *obj) const
         obj_name = obj_repr->name();
         obj_id = obj_repr->attribute("id");
     }
-    std::printf("WARNING: Ignoring recursive clippath reference "
-                "<%s clippath=\"%s\"> in <%s id=\"%s\">",
-                owner_name, owner_clippath,
-                obj_name, obj_id);
+    std::cerr << "WARNING: Ignoring recursive clippath reference "
+        << "<" << (owner_name ? owner_name : "(null)") << " clippath=\"" <<  (owner_clippath ? owner_clippath : "(null)") << "\">"
+        << " in <" << (obj_name ? obj_name : "(null)") << " id=\"" << (obj_id ? obj_id : "(null)") << "\">" << std::endl;
 
     return false;
 }
diff --git a/src/object/sp-mask.cpp b/src/object/sp-mask.cpp
index b0f7fd94a5e9cc91a0bee9a840fc87605e08f549..17363f9fa5ef802f23f451a708560e7747bd4220 100644
--- a/src/object/sp-mask.cpp
+++ b/src/object/sp-mask.cpp
@@ -289,10 +289,9 @@ bool SPMaskReference::_acceptObject(SPObject *obj) const
         obj_name = obj_repr->name();
         obj_id = obj_repr->attribute("id");
     }
-    std::printf("WARNING: Ignoring recursive mask reference "
-               "<%s mask=\"%s\"> in <%s id=\"%s\">",
-               owner_name, owner_mask,
-               obj_name, obj_id);
+    std::cerr << "WARNING: Ignoring recursive mask reference "
+        << "<" << (owner_name ? owner_name : "(null)") << " mask=\"" <<  (owner_mask ? owner_mask : "(null)") << "\">"
+        << " in <" << (obj_name ? obj_name : "(null)") << " id=\"" << (obj_id ? obj_id : "(null)") << "\">" << std::endl;
 
     return false;
 }