From e08fb78754dcc3414b1ee8bd35b692ac75da4fbc Mon Sep 17 00:00:00 2001
From: Sean Gillies <sean@mapbox.com>
Date: Thu, 8 Jan 2015 12:38:57 -0700
Subject: [PATCH] Get fallback nodata value from dest.

---
 rasterio/rio/merge.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rasterio/rio/merge.py b/rasterio/rio/merge.py
index d6e647cb..b824a2fd 100644
--- a/rasterio/rio/merge.py
+++ b/rasterio/rio/merge.py
@@ -39,7 +39,7 @@ def merge(ctx, files, driver):
                 dest = np.zeros((first.count,) + first.shape, 
                     dtype=first.dtypes[0])
 
-            nodataval = 0.0
+            nodataval = next(dest.flat)
             if os.path.exists(output):
                 dst = rasterio.open(output, 'r+')
                 nodataval = dst.nodatavals[0] or nodataval