diff --git a/chrome/content/zotero/import/mendeley/mendeleyImport.js b/chrome/content/zotero/import/mendeley/mendeleyImport.js
index 92cd68e471..9d6613e2e6 100644
--- a/chrome/content/zotero/import/mendeley/mendeleyImport.js
+++ b/chrome/content/zotero/import/mendeley/mendeleyImport.js
@@ -1626,13 +1626,19 @@ Zotero_Import_Mendeley.prototype._saveAnnotations = async function (annotations,
 			let file = await attachmentItem.getFilePathAsync();
 			if (file) {
 				// Fix blank PDF attachment MIME type from previous imports
+				let type = 'application/pdf';
 				if (!attachmentItem.attachmentContentType) {
-					let type = 'application/pdf';
 					if (Zotero.MIME.sniffForMIMEType(await Zotero.File.getSample(file)) == type) {
 						attachmentItem.attachmentContentType = type;
 						await attachmentItem.saveTx(this._saveOptions);
 					}
 				}
+
+				if (attachmentItem.attachmentContentType !== type) {
+					Zotero.debug(`Skipping ${annotations.length} annotations for non-PDF (${attachmentItem.attachmentContentType}) file ${file}`);
+					// do not attempt to import annotations for non-PDF files
+					return;
+				}
 				
 				let annotationMap = new Map();
 				for (let annotation of annotations) {