diff --git a/chrome/content/zotero/xpcom/data/item.js b/chrome/content/zotero/xpcom/data/item.js
index 87edb15069..5a7e4585db 100644
--- a/chrome/content/zotero/xpcom/data/item.js
+++ b/chrome/content/zotero/xpcom/data/item.js
@@ -3233,10 +3233,11 @@ for (let name of ['lastProcessedModificationTime', 'pageIndex']) {
 					}
 					if (parseInt(val) != val || val < 0) {
 						Zotero.debug(val, 2);
-						throw new Error(`${prop} must be a timestamp in milliseconds`);
+						throw new Error(`${prop} must be a timestamp in seconds`);
 					}
-					if (val < 10000000000) {
-						Zotero.logError("attachmentlastProcesedModificationTime should be a timestamp in milliseconds "
+					// Change before 2065!
+					if (val > 3000000000) {
+						throw new Error(`${prop} should be a timestamp in seconds `
 							+ "-- " + val + " given");
 					}
 					break;
diff --git a/chrome/content/zotero/xpcom/pdfWorker/manager.js b/chrome/content/zotero/xpcom/pdfWorker/manager.js
index 8a911c0558..a9e0693427 100644
--- a/chrome/content/zotero/xpcom/pdfWorker/manager.js
+++ b/chrome/content/zotero/xpcom/pdfWorker/manager.js
@@ -252,7 +252,9 @@ class PDFWorker {
 					reader.toggleImportPrompt(attachment.attachmentHasUnimportedAnnotations);
 				}
 			}
-			attachment.attachmentLastProcessedModificationTime = await attachment.attachmentModificationTime;
+			attachment.attachmentLastProcessedModificationTime = Math.floor(
+				await attachment.attachmentModificationTime / 1000
+			);
 			await attachment.saveTx();
 			return annotations.length;
 		});
diff --git a/chrome/content/zotero/xpcom/reader.js b/chrome/content/zotero/xpcom/reader.js
index 83c192c579..0df7ee5d35 100644
--- a/chrome/content/zotero/xpcom/reader.js
+++ b/chrome/content/zotero/xpcom/reader.js
@@ -811,7 +811,7 @@ class Reader {
 	async triggerAnnotationsImportCheck(itemID) {
 		let item = await Zotero.Items.getAsync(itemID);
 		let mtime = await item.attachmentModificationTime;
-		if (item.attachmentLastProcessedModificationTime < mtime) {
+		if (item.attachmentLastProcessedModificationTime < Math.floor(mtime / 1000)) {
 			await Zotero.PDFWorker.import(itemID, false);
 		}
 	}
diff --git a/test/tests/itemTest.js b/test/tests/itemTest.js
index 49c8e45c7c..26907c18b6 100644
--- a/test/tests/itemTest.js
+++ b/test/tests/itemTest.js
@@ -1191,7 +1191,7 @@ describe("Zotero.Item", function () {
 			var item = await createDataObject('item');
 			var attachment = await importFileAttachment('test.pdf', { parentID: item.id });
 			
-			var mtime = Date.now();
+			var mtime = Math.floor(Date.now() / 1000);
 			attachment.attachmentLastProcessedModificationTime = mtime;
 			await attachment.saveTx();
 			
@@ -1512,7 +1512,7 @@ describe("Zotero.Item", function () {
 			);
 			assert.lengthOf(annotationIDs, 1);
 			
-			attachment.attachmentLastProcessedModificationTime = Date.now();
+			attachment.attachmentLastProcessedModificationTime = Math.floor(Date.now() / 1000);
 			await attachment.saveTx();
 			
 			annotationIDs = await Zotero.DB.columnQueryAsync(