diff --git a/doc/source/transform_github_links.py b/doc/source/transform_github_links.py
index 695d51d..ad862dd 100644
--- a/doc/source/transform_github_links.py
+++ b/doc/source/transform_github_links.py
@@ -73,16 +73,17 @@ def transform_github_links(app, doctree, fromdocname):
         # Replace the suffix with the correct target format file ending,
         # but only if the link ends with both the correct source suffix
         # and refers to a local file.
-        if link.endswith(source_suffix):
-            # absolute paths are considered relative to repo
-            if link.startswith("/"):
-                basepath = ""
-            # relative paths are against the current doctree source path
-            else:
-                basepath = doc_dir
-            if os.path.exists(os.path.join(basepath, link)):
-                node['refuri'] = (link[:-len(source_suffix)] + target_format +
-                                  anchor)
+        for src_suffix in source_suffix:
+            if link.endswith(src_suffix):
+                # absolute paths are considered relative to repo
+                if link.startswith("/"):
+                    basepath = ""
+                # relative paths are against the current doctree source path
+                else:
+                    basepath = doc_dir
+                if os.path.exists(os.path.join(basepath, link)):
+                    node['refuri'] = (link[:-len(source_suffix)] + target_format +
+                                    anchor)
 
 
 def setup(app):
diff --git a/test-requirements.txt b/test-requirements.txt
index 62e3253..e2cbaaf 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,7 +1,7 @@
 hacking>=0.11.0,<0.12  # Apache-2.0
 loremipsum
 mock!=1.1.1,<=1.3.0
-Sphinx>=1.1.2,<1.2
+sphinx>=1.5.1  # BSD
 discover
 coverage>=3.6  # Apache-2.0
 fixtures>=0.3.14