diff --git a/fuzz/CMakeLists.txt b/fuzz/CMakeLists.txt
index 0b24bc8..288c168 100644
--- a/fuzz/CMakeLists.txt
+++ b/fuzz/CMakeLists.txt
@@ -156,6 +156,7 @@ set(CORPUS_OTHER
   394129398.fuzz
   394463491.fuzz
   398060137.fuzz
+  409905355.fuzz
 )
 
 set(CORPUS_DIR ${CMAKE_CURRENT_BINARY_DIR}/qpdf_corpus)
diff --git a/fuzz/qpdf_extra/409905355.fuzz b/fuzz/qpdf_extra/409905355.fuzz
new file mode 100644
index 0000000..8d5361e
--- /dev/null
+++ b/fuzz/qpdf_extra/409905355.fuzz
diff --git a/fuzz/qtest/fuzz.test b/fuzz/qtest/fuzz.test
index 6bde52e..12229d0 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 = 93;       # increment when adding new files
+my $n_qpdf_files = 94;       # increment when adding new files
 
 my @fuzzers = (
     ['ascii85' => 1],
diff --git a/libqpdf/QPDFFormFieldObjectHelper.cc b/libqpdf/QPDFFormFieldObjectHelper.cc
index 77d1e84..4ce81b7 100644
--- a/libqpdf/QPDFFormFieldObjectHelper.cc
+++ b/libqpdf/QPDFFormFieldObjectHelper.cc
@@ -585,17 +585,16 @@ ValueSetter::writeAppearance()
             int wanted_first = QIntC::to_int(found_idx) - 1;
             int wanted_last = QIntC::to_int(found_idx + max_rows) - 2;
             QTC::TC("qpdf", "QPDFFormFieldObjectHelper list found");
-            while (wanted_first < 0) {
+            if (wanted_first < 0) {
                 QTC::TC("qpdf", "QPDFFormFieldObjectHelper list first too low");
-                ++wanted_first;
-                ++wanted_last;
+                wanted_last -= wanted_first;
+                wanted_first = 0;
             }
-            while (wanted_last >= QIntC::to_int(nopt)) {
+            if (wanted_last >= QIntC::to_int(nopt)) {
                 QTC::TC("qpdf", "QPDFFormFieldObjectHelper list last too high");
-                if (wanted_first > 0) {
-                    --wanted_first;
-                }
-                --wanted_last;
+                auto diff = wanted_last - QIntC::to_int(nopt) + 1;
+                wanted_first = std::max(0, wanted_first - diff);
+                wanted_last -= diff;
             }
             highlight = true;
             highlight_idx = found_idx - QIntC::to_size(wanted_first);