diff --git a/libqpdf/QPDF_linearization.cc b/libqpdf/QPDF_linearization.cc
index 660290f..a63f050 100644
--- a/libqpdf/QPDF_linearization.cc
+++ b/libqpdf/QPDF_linearization.cc
@@ -1288,24 +1288,20 @@ QPDF::calculateLinearizationData(T const& object_stream_data)
     for (size_t i = 0; i < toS(npages); ++i) {
         QPDFObjectHandle thumb = pages.at(i).getKey("/Thumb");
         thumb = getUncompressedObject(thumb, object_stream_data);
-        if (!thumb.isNull()) {
-            // Output the thumbnail itself
-            QPDFObjGen thumb_og(thumb.getObjGen());
-            if (lc_thumbnail_private.contains(thumb_og)) {
-                lc_thumbnail_private.erase(thumb_og);
-                m->part9.push_back(thumb);
-            } else {
-                // No internal error this time...there's nothing to stop this object from having
-                // been referred to somewhere else outside of a page's /Thumb, and if it had been,
-                // there's nothing to prevent it from having been in some set other than
-                // lc_thumbnail_private.
-            }
-            std::set<QPDFObjGen>& ogs = m->obj_user_to_objects[ObjUser(ObjUser::ou_thumb, toI(i))];
-            for (auto const& og: ogs) {
-                if (lc_thumbnail_private.contains(og)) {
-                    lc_thumbnail_private.erase(og);
-                    m->part9.push_back(getObject(og));
-                }
+        QPDFObjGen thumb_og(thumb.getObjGen());
+        // Output the thumbnail itself
+        if (lc_thumbnail_private.erase(thumb_og) && !thumb.isNull()) {
+            m->part9.emplace_back(thumb);
+        } else {
+            // No internal error this time...there's nothing to stop this object from having
+            // been referred to somewhere else outside of a page's /Thumb, and if it had been,
+            // there's nothing to prevent it from having been in some set other than
+            // lc_thumbnail_private.
+        }
+        std::set<QPDFObjGen>& ogs = m->obj_user_to_objects[ObjUser(ObjUser::ou_thumb, toI(i))];
+        for (auto const& og: ogs) {
+            if (lc_thumbnail_private.erase(og)) {
+                m->part9.emplace_back(getObject(og));
             }
         }
     }
diff --git a/qpdf/qtest/qpdf/issue-1503.out b/qpdf/qtest/qpdf/issue-1503.out
new file mode 100644
index 0000000..a57585c
--- /dev/null
+++ b/qpdf/qtest/qpdf/issue-1503.out
@@ -0,0 +1,101 @@
+WARNING: issue-1503.pdf: can't find PDF header
+WARNING: issue-1503.pdf: file is damaged
+WARNING: issue-1503.pdf: can't find startxref
+WARNING: issue-1503.pdf: Attempting to reconstruct cross-reference table
+WARNING: issue-1503.pdf (object 31 0, offset 813): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 31 0, offset 851): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 31 0, offset 856): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 31 0, offset 861): unexpected 'endobj' or 'endstream' while reading object; giving up on reading object
+WARNING: issue-1503.pdf (object 31 0, offset 871): expected endobj
+WARNING: issue-1503.pdf (object 38 0, offset 1126): unexpected 'endobj' or 'endstream' while reading object; giving up on reading object
+WARNING: issue-1503.pdf (object 38 0, offset 1133): expected endobj
+WARNING: issue-1503.pdf (object 40 0, offset 1195): unexpected array close token; giving up on reading object
+WARNING: issue-1503.pdf (object 40 0, offset 1198): expected endobj
+WARNING: issue-1503.pdf (object 41 0, offset 1359): stream dictionary lacks /Length key
+WARNING: issue-1503.pdf (object 41 0, offset 1411): attempting to recover stream length
+WARNING: issue-1503.pdf (object 41 0, offset 1411): recovered stream length: 54
+WARNING: issue-1503.pdf (object 44 0, offset 1744): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 44 0, offset 1767): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 44 0, offset 1775): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 44 0, offset 1779): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 44 0, offset 1814): name with stray # will not work with PDF >= 1.2
+WARNING: issue-1503.pdf (object 44 0, offset 1821): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 44 0, offset 1826): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 44 0, offset 1826): too many errors; giving up on reading object
+WARNING: issue-1503.pdf (object 44 0, offset 1829): expected endobj
+WARNING: issue-1503.pdf (object 46 0, offset 1923): unexpected array close token; giving up on reading object
+WARNING: issue-1503.pdf (object 46 0, offset 1926): expected endobj
+WARNING: issue-1503.pdf (object 47 0, offset 2087): stream dictionary lacks /Length key
+WARNING: issue-1503.pdf (object 47 0, offset 2139): attempting to recover stream length
+WARNING: issue-1503.pdf (object 47 0, offset 2139): recovered stream length: 54
+WARNING: issue-1503.pdf (object 49 0, offset 2256): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 49 0, offset 2271): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 49 0, offset 2241): expected dictionary keys but found non-name objects; ignoring
+WARNING: issue-1503.pdf (object 50 0, offset 2483): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 50 0, offset 2453): expected dictionary keys but found non-name objects; ignoring
+WARNING: issue-1503.pdf (object 50 0, offset 2450): stream dictionary lacks /Length key
+WARNING: issue-1503.pdf (object 50 0, offset 2530): attempting to recover stream length
+WARNING: issue-1503.pdf (object 50 0, offset 2530): unable to recover stream data; treating stream as empty
+WARNING: issue-1503.pdf (object 114 0, offset 2693): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 114 0, offset 2697): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 114 0, offset 2652): expected dictionary keys but found non-name objects; ignoring
+WARNING: issue-1503.pdf (object 114 0, offset 2649): stream dictionary lacks /Length key
+WARNING: issue-1503.pdf (object 114 0, offset 2783): attempting to recover stream length
+WARNING: issue-1503.pdf (object 114 0, offset 2783): recovered stream length: 84
+WARNING: issue-1503.pdf (object 116 0, offset 2927): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 116 0, offset 2914): stream dictionary lacks /Length key
+WARNING: issue-1503.pdf (object 116 0, offset 3101): attempting to recover stream length
+WARNING: issue-1503.pdf (object 116 0, offset 3101): recovered stream length: 84
+WARNING: issue-1503.pdf (object 118 0, offset 3271): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 118 0, offset 3235): expected dictionary keys but found non-name objects; ignoring
+WARNING: issue-1503.pdf (object 118 0, offset 3232): /Length key in stream dictionary is not an integer
+WARNING: issue-1503.pdf (object 118 0, offset 3370): attempting to recover stream length
+WARNING: issue-1503.pdf (object 118 0, offset 3370): recovered stream length: 102
+WARNING: issue-1503.pdf (object 120 0, offset 3519): stream dictionary lacks /Length key
+WARNING: issue-1503.pdf (object 120 0, offset 3653): attempting to recover stream length
+WARNING: issue-1503.pdf (object 120 0, offset 3653): unable to recover stream data; treating stream as empty
+WARNING: issue-1503.pdf (object 122 0, offset 3723): expected endobj
+WARNING: issue-1503.pdf (object 151 0, offset 3836): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 151 0, offset 3958): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 152 0, offset 4088): parse error while reading object
+WARNING: issue-1503.pdf (object 152 0, offset 4088): unexpected EOF
+WARNING: issue-1503.pdf (object 152 0, offset 4088): expected endobj
+WARNING: issue-1503.pdf (object 152 0, offset 4088): EOF after endobj
+WARNING: issue-1503.pdf (object 155 0, offset 162): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 155 0, offset 342): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 155 0, offset 345): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 155 0, offset 334): expected dictionary keys but found non-name objects; ignoring
+WARNING: issue-1503.pdf (object 155 0, offset 152): expected dictionary keys but found non-name objects; ignoring
+WARNING: issue-1503.pdf (object 155 0, offset 405): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 155 0, offset 479): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 155 0, offset 485): unknown token while reading object; treating as null
+WARNING: issue-1503.pdf (object 155 0, offset 136): expected dictionary keys but found non-name objects; ignoring
+WARNING: issue-1503.pdf (object 173 0, offset 574): expected endobj
+WARNING: issue-1503.pdf: unable to find trailer dictionary while recovering damaged file
+WARNING: object 157 0: Pages tree includes non-dictionary object; ignoring
+WARNING: issue-1503.pdf, object 151 0 at offset 3831: Pages tree includes non-dictionary object; ignoring
+WARNING: issue-1503.pdf, object 151 0 at offset 3834: Pages tree includes non-dictionary object; ignoring
+Pages tree includes non-dictionary object; ignoring
+WARNING: object 22 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 25 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 28 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 31 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 34 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 37 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 40 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 46 0: Pages tree includes non-dictionary object; ignoring
+WARNING: issue-1503.pdf, object 49 0 at offset 2241: kid 13 (from 0) MediaBox is undefined; setting to letter / ANSI A
+WARNING: object 52 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 55 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 58 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 61 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 64 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 67 0: Pages tree includes non-dictionary object; ignoring
+WARNING: issue-1503.pdf, object 151 0 at offset 3953: Pages tree includes non-dictionary object; ignoring
+Pages tree includes non-dictionary object; ignoring
+WARNING: object 73 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 76 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 79 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 82 0: Pages tree includes non-dictionary object; ignoring
+WARNING: object 85 0: Pages tree includes non-dictionary object; ignoring
+qpdf: operation succeeded with warnings; resulting file may have some problems
diff --git a/qpdf/qtest/qpdf/issue-1503.pdf b/qpdf/qtest/qpdf/issue-1503.pdf
new file mode 100644
index 0000000..6a327ba
--- /dev/null
+++ b/qpdf/qtest/qpdf/issue-1503.pdf
diff --git a/qpdf/qtest/specific-bugs.test b/qpdf/qtest/specific-bugs.test
index 1613224..6668a14 100644
--- a/qpdf/qtest/specific-bugs.test
+++ b/qpdf/qtest/specific-bugs.test
@@ -38,6 +38,7 @@ my @bug_tests = (
     ["263", "empty xref stream", 2],
     ["335a", "ozz-fuzz-12152", 2],
     ["335b", "ozz-fuzz-14845", 2],
+    ["1503", "linearize with bad outlines", 3, "--linearize"],
     ["fuzz-16214", "stream in object stream", 3, "--preserve-unreferenced"],
     # When adding to this list, consider adding to CORPUS_FROM_TEST in
     # fuzz/CMakeLists.txt and updating the count in