diff --git a/mercurial/revlogutils/deltas.py b/mercurial/revlogutils/deltas.py
--- a/mercurial/revlogutils/deltas.py
+++ b/mercurial/revlogutils/deltas.py
@@ -932,6 +932,21 @@ class deltacomputer(object):
 
     def _builddeltainfo(self, revinfo, base, fh):
         # can we use the cached delta?
+        revlog = self.revlog
+        chainbase = revlog.chainbase(base)
+        if revlog._generaldelta:
+            deltabase = base
+        else:
+            deltabase = chainbase
+        snapshotdepth = None
+        if revlog._sparserevlog and deltabase == nullrev:
+            snapshotdepth = 0
+        elif revlog._sparserevlog and revlog.issnapshot(deltabase):
+            # A delta chain should always be one full snapshot,
+            # zero or more semi-snapshots, and zero or more deltas
+            p1, p2 = revlog.rev(revinfo.p1), revlog.rev(revinfo.p2)
+            if deltabase not in (p1, p2) and revlog.issnapshot(deltabase):
+                snapshotdepth = len(revlog._deltachain(deltabase)[0])
         delta = None
         if revinfo.cachedelta:
             cachebase, cachediff = revinfo.cachedelta
@@ -945,31 +960,14 @@ class deltacomputer(object):
                 delta = revinfo.cachedelta[1]
         if delta is None:
             delta = self._builddeltadiff(base, revinfo, fh)
-        revlog = self.revlog
         header, data = revlog.compress(delta)
         deltalen = len(header) + len(data)
-        chainbase = revlog.chainbase(base)
         offset = revlog.end(len(revlog) - 1)
         dist = deltalen + offset - revlog.start(chainbase)
-        if revlog._generaldelta:
-            deltabase = base
-        else:
-            deltabase = chainbase
         chainlen, compresseddeltalen = revlog._chaininfo(base)
         chainlen += 1
         compresseddeltalen += deltalen
 
-        revlog = self.revlog
-        snapshotdepth = None
-        if deltabase == nullrev:
-            snapshotdepth = 0
-        elif revlog._sparserevlog and revlog.issnapshot(deltabase):
-            # A delta chain should always be one full snapshot,
-            # zero or more semi-snapshots, and zero or more deltas
-            p1, p2 = revlog.rev(revinfo.p1), revlog.rev(revinfo.p2)
-            if deltabase not in (p1, p2) and revlog.issnapshot(deltabase):
-                snapshotdepth = len(revlog._deltachain(deltabase)[0])
-
         return _deltainfo(dist, deltalen, (header, data), deltabase,
                           chainbase, chainlen, compresseddeltalen,
                           snapshotdepth)