diff --git a/src/geotiffimage.js b/src/geotiffimage.js
index aff618ca..7ece4055 100644
--- a/src/geotiffimage.js
+++ b/src/geotiffimage.js
@@ -295,8 +295,7 @@ class GeoTIFFImage {
   }
 
   getReaderForSample(sampleIndex) {
-    const format = this.fileDirectory.SampleFormat
-      ? this.fileDirectory.SampleFormat[sampleIndex] : 1;
+    const format = this.fileDirectory.SampleFormat?.[sampleIndex] ?? 1;
     const bitsPerSample = this.fileDirectory.BitsPerSample[sampleIndex];
     switch (format) {
       case 1: // unsigned integer data