Index: nautilus-thumbnails.c
===================================================================
--- nautilus-thumbnails.c	(revision 13055)
+++ nautilus-thumbnails.c	(working copy)
@@ -286,7 +286,12 @@
 		args->base_size = size;                        
 	} else if (args->base_size == 0) {
 		if (args->is_thumbnail) {
-			args->base_size = 128 * NAUTILUS_ICON_SIZE_STANDARD / thumbnail_icon_size;
+			if (size > 128 * NAUTILUS_ICON_SIZE_STANDARD / thumbnail_icon_size) {
+				args->base_size = 128 * NAUTILUS_ICON_SIZE_STANDARD / thumbnail_icon_size;
+			} else {
+				/* Don't scale small thumbnails */
+				args->base_size = NAUTILUS_ICON_SIZE_STANDARD;
+			}			
 		} else {
 			if (size > args->nominal_size * thumbnail_icon_size / NAUTILUS_ICON_SIZE_STANDARD) {
 				args->base_size = size * NAUTILUS_ICON_SIZE_STANDARD / thumbnail_icon_size;
