diff --git a/i/lib/crop/cropwidget.cpp b/lib/crop/cropwidget.cpp
--- a/i/lib/crop/cropwidget.cpp
+++ b/lib/crop/cropwidget.cpp
@@ -58,7 +58,12 @@
 static QSize ratio(const QSize &size)
 {
     const int divisor = gcd(size.width(), size.height());
-    return size / divisor;
+    // may happen when the crop tool is activated after the image was already cropped to a zero sized image
+    if (divisor == 0) {
+        return {0, 0};
+    } else {
+        return size / divisor;
+    }
 }

 struct CropWidgetPrivate : public QWidget