diff --git a/include/qpdf/QPDF.hh b/include/qpdf/QPDF.hh
index 2ee2bb34..9cfcb2c2 100644
--- a/include/qpdf/QPDF.hh
+++ b/include/qpdf/QPDF.hh
@@ -391,8 +391,8 @@ class QPDF
     void swapObjects(int objid1, int generation1, int objid2, int generation2);
 
     // Replace a reserved object.  This is a wrapper around replaceObject but it guarantees that the
-    // underlying object is a reserved object.  After this call, reserved will be a reference to
-    // replacement.
+    // underlying object is a reserved object or a null object.  After this call, reserved will
+    // be a reference to replacement.
     QPDF_DLL
     void replaceReserved(QPDFObjectHandle reserved, QPDFObjectHandle replacement);
 
diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index 45bd1847..739ad7ce 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -1948,7 +1948,10 @@ void
 QPDF::replaceReserved(QPDFObjectHandle reserved, QPDFObjectHandle replacement)
 {
     QTC::TC("qpdf", "QPDF replaceReserved");
-    reserved.assertReserved();
+    auto tc = reserved.getTypeCode();
+    if (!(tc == ::ot_reserved || tc == ::ot_null)) {
+        throw std::logic_error("replaceReserved called with non-reserverd object");
+    }
     replaceObject(reserved.getObjGen(), replacement);
 }