diff --git a/loopy/kernel/tools.py b/loopy/kernel/tools.py
index b8be6191d933899dbac2f37eb5b85267defa7690..2f32d94f662fe59d23ffb06dd13ade4a057304aa 100644
--- a/loopy/kernel/tools.py
+++ b/loopy/kernel/tools.py
@@ -482,7 +482,8 @@ def get_dot_dependency_graph(kernel, iname_cluster=True, use_insn_id=False):
 
     for insn in kernel.instructions:
         if isinstance(insn, MultiAssignmentBase):
-            op = "%s <- %s" % (insn.assignees, insn.expression)
+            lhs = ', '.join(str(assignee) for assignee in insn.assignees)
+            op = "%s <- %s" % (lhs, insn.expression)
             if len(op) > 200:
                 op = op[:200] + "..."