diff --git a/core/src/main/java/com/google/zxing/qrcode/detector/Detector.java b/core/src/main/java/com/google/zxing/qrcode/detector/Detector.java
index 9648883bb..8cbf2df2d 100644
--- a/core/src/main/java/com/google/zxing/qrcode/detector/Detector.java
+++ b/core/src/main/java/com/google/zxing/qrcode/detector/Detector.java
@@ -211,7 +211,7 @@ public class Detector {
         dimension--;
         break;
       case 3:
-        throw NotFoundException.getNotFoundInstance();
+        dimension = dimension - 2;
     }
     return dimension;
   }