diff --git a/tools/viewer/Viewer.cpp b/tools/viewer/Viewer.cpp
index 61cc025..198d63d 100644
--- a/tools/viewer/Viewer.cpp
+++ b/tools/viewer/Viewer.cpp
@@ -1156,7 +1156,9 @@
 }
 
 void Viewer::onResize(int width, int height) {
-    fSlides[fCurrentSlide]->resize(width, height);
+    if (fCurrentSlide >= 0) {
+        fSlides[fCurrentSlide]->resize(width, height);
+    }
 }
 
 SkPoint Viewer::mapEvent(float x, float y) {