diff --git a/config.def.h b/config.def.h
index d491788..c09097d 100644
--- a/config.def.h
+++ b/config.def.h
@@ -77,7 +77,7 @@ static const bool ALPHA_LAYER = false;
 static const int thumb_sizes[] = { 32, 64, 96, 128, 160, 256, 512, 800, 1024 };
 
 /* thumbnail size at startup, index into thumb_sizes[]: */
-static const int THUMB_SIZE = 3;
+static const int THUMB_SIZE = 4;
 
 #endif
 #ifdef INCLUDE_MAPPINGS_CONFIG