diff --git a/mercurial/graphmod.py b/mercurial/graphmod.py
--- a/mercurial/graphmod.py
+++ b/mercurial/graphmod.py
@@ -181,7 +181,7 @@ def asciiedges(type, char, lines, seen, 
     ncols = len(seen)
     nextseen = seen[:]
     nextseen[nodeidx:nodeidx + 1] = newparents
-    edges = [(nodeidx, nextseen.index(p)) for p in knownparents]
+    edges = [(nodeidx, nextseen.index(p)) for p in knownparents if p != nullrev]
 
     while len(newparents) > 2:
         # ascii() only knows how to add or remove a single column between two
diff --git a/tests/test-glog.t b/tests/test-glog.t
--- a/tests/test-glog.t
+++ b/tests/test-glog.t
@@ -2109,4 +2109,12 @@ The almost-empty template should do some
   o
   
 
+issue3772
+
+  $ hg glog -r :null
+  o  changeset:   -1:000000000000
+     user:
+     date:        Thu Jan 01 00:00:00 1970 +0000
+  
+
   $ cd ..