diff --git a/jax/_src/interpreters/batching.py b/jax/_src/interpreters/batching.py
index ed7a6f86a35e..5039269b0a6f 100644
--- a/jax/_src/interpreters/batching.py
+++ b/jax/_src/interpreters/batching.py
@@ -333,13 +333,18 @@ def get_axis_primitive_batcher(self, primitive, frame):
         frame.size, frame.name, frame.main_trace.trace_type)
 
   def get_frame(self, vals, dims) -> core.AxisEnvFrame:
-    frame = core.axis_frame(self.axis_name, self.main)
-    assert frame.main_trace is self.main
     if any(d is not not_mapped for d in dims):
       sizes = (x.shape[d] if type(d) is int else len(d.segment_lengths)
                for x, d in zip(vals, dims) if d is not not_mapped)
-      data_axis_size, = core.dedup_referents(sizes)
-      assert data_axis_size == frame.size
+      axis_size, = core.dedup_referents(sizes)
+    else:
+      axis_size = None  # can't be inferred from data
+    if self.axis_name is core.no_axis_name:
+      assert axis_size is not None  # must be inferrable from data
+      return core.AxisEnvFrame(self.axis_name, axis_size, self.main)
+    frame = core.axis_frame(self.axis_name, self.main)
+    assert axis_size is None or axis_size == frame.size, (axis_size, frame.size)
+    assert frame.main_trace is self.main
     return frame
 
   def process_primitive(self, primitive, tracers, params):