diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index ae23bacf142..5ed46c3278d 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -338,6 +338,7 @@ def fetch(self):
         errors = []
         for url in self.candidate_urls:
             if not web_util.url_exists(url, self.curl):
+                tty.debug("URL does not exist: " + url)
                 continue
 
             try:
diff --git a/lib/spack/spack/util/web.py b/lib/spack/spack/util/web.py
index 202cb8a5044..fa4119f9173 100644
--- a/lib/spack/spack/util/web.py
+++ b/lib/spack/spack/util/web.py
@@ -444,7 +444,8 @@ def url_exists(url, curl=None):
     try:
         read_from_url(url)
         return True
-    except (SpackWebError, URLError):
+    except (SpackWebError, URLError) as e:
+        tty.debug("Failure reading URL: " + str(e))
         return False