diff --git a/fuzz/CMakeLists.txt b/fuzz/CMakeLists.txt
index 0b81397..136a518 100644
--- a/fuzz/CMakeLists.txt
+++ b/fuzz/CMakeLists.txt
@@ -164,6 +164,7 @@ set(CORPUS_OTHER
   4720043549327360.fuzz
   5109284021272576.fuzz
   5828408539152384.fuzz
+  6310410941956096.fuzz
   6489005569146880.fuzz
 )
 
diff --git a/fuzz/qpdf_extra/6310410941956096.fuzz b/fuzz/qpdf_extra/6310410941956096.fuzz
new file mode 100644
index 0000000..9d7851a
--- /dev/null
+++ b/fuzz/qpdf_extra/6310410941956096.fuzz
diff --git a/fuzz/qtest/fuzz.test b/fuzz/qtest/fuzz.test
index ecafb06..dba9984 100644
--- a/fuzz/qtest/fuzz.test
+++ b/fuzz/qtest/fuzz.test
@@ -11,7 +11,7 @@ my $td = new TestDriver('fuzz');
 
 my $qpdf_corpus = $ENV{'QPDF_FUZZ_CORPUS'} || die "must set QPDF_FUZZ_CORPUS";
 
-my $n_qpdf_files = 102;       # increment when adding new files
+my $n_qpdf_files = 103;       # increment when adding new files
 
 my @fuzzers = (
     ['ascii85' => 1],
diff --git a/libqpdf/NNTree.cc b/libqpdf/NNTree.cc
index 27da4ae..372f7c6 100644
--- a/libqpdf/NNTree.cc
+++ b/libqpdf/NNTree.cc
@@ -666,7 +666,7 @@ NNTreeImpl::repair()
     NNTreeImpl repl(qpdf, new_node, key_type, value_valid, false);
     std::map<QPDFObjectHandle, QPDFObjectHandle, Cmp> items;
     for (auto const& [key, value]: *this) {
-        if (key && value) {
+        if (key && value && repl.keyValid(key) && repl.value_valid(value) ) {
             items.insert_or_assign(key, value);
         }
     }