diff --git a/test/test_fmm.py b/test/test_fmm.py
index c85759fef3f2c6bf6457cb55185ed3f15d32f369..0d8f36d81979de64103c50f29ac21ecc46625abf 100644
--- a/test/test_fmm.py
+++ b/test/test_fmm.py
@@ -111,8 +111,8 @@ def test_sumpy_fmm(ctx_getter, knl, local_expn_class, mpole_expn_class):
     ctx = ctx_getter()
     queue = cl.CommandQueue(ctx)
 
-    nsources = 500
-    ntargets = 50
+    nsources = 1000
+    ntargets = 300
     dtype = np.float64
 
     from boxtree.tools import (
@@ -225,7 +225,7 @@ def test_sumpy_fmm(ctx_getter, knl, local_expn_class, mpole_expn_class):
         pot = pot.get()
         ref_pot = ref_pot.get()
 
-        rel_err = la.norm(pot - ref_pot) / la.norm(ref_pot)
+        rel_err = la.norm(pot - ref_pot, np.inf) / la.norm(ref_pot, np.inf)
         logger.info("order %d -> relative l2 error: %g" % (order, rel_err))
 
         pconv_verifier.add_data_point(order, rel_err)