diff --git a/src/api/openLibrary.test.ts b/src/api/openLibrary.test.ts
index 74cba71..1a6643e 100644
--- a/src/api/openLibrary.test.ts
+++ b/src/api/openLibrary.test.ts
@@ -56,6 +56,30 @@ describe("searchBooksBySubject", () => {
     });
   });
 
+  it("treats a publication year of 0 as missing", async () => {
+    const responseWithInvalidYear = {
+      docs: [
+        {
+          key: "/works/OL3",
+          title: "Unknown Publication Year",
+          first_publish_year: 0,
+        },
+      ],
+    };
+
+    vi.stubGlobal(
+      "fetch",
+      vi.fn().mockResolvedValue({
+        ok: true,
+        json: async () => responseWithInvalidYear,
+      }),
+    );
+
+    const books = await searchBooksBySubject("history");
+
+    expect(books[0].firstPublishYear).toBeNull();
+  });
+
   it("requests the configured limit and only the needed fields", async () => {
     const fetchMock = vi.fn().mockResolvedValue({ ok: true, json: async () => ({ docs: [] }) });
     vi.stubGlobal("fetch", fetchMock);
diff --git a/src/api/openLibrary.ts b/src/api/openLibrary.ts
index 707ba1c..8eee597 100644
--- a/src/api/openLibrary.ts
+++ b/src/api/openLibrary.ts
@@ -30,7 +30,7 @@ function toBook(doc: OpenLibrarySearchDoc): Book {
     key: doc.key,
     title: doc.title,
     authors: doc.author_name ?? [],
-    firstPublishYear: doc.first_publish_year ?? null,
+    firstPublishYear: yearOrNull(doc.first_publish_year),
     averageRating: numberOrNull(doc.ratings_average),
     ratingsCount: numberOrNull(doc.ratings_count),
     coverId: doc.cover_i ?? null,
@@ -38,6 +38,10 @@ function toBook(doc: OpenLibrarySearchDoc): Book {
   };
 }
 
+function yearOrNull(value: number | undefined): number | null {
+  return typeof value === "number" && Number.isFinite(value) && value > 0 ? value : null;
+}
+
 function numberOrNull(value: number | undefined): number | null {
   return typeof value === "number" && Number.isFinite(value) ? value : null;
 }