diff --git a/boxtree/traversal.py b/boxtree/traversal.py
index 6f24e5b5769485cb6b9ca3fecfc6bb92397b2f3c..3448ee56a0f359160cc0bfcec17957029b56cbba 100644
--- a/boxtree/traversal.py
+++ b/boxtree/traversal.py
@@ -136,8 +136,8 @@ TRAVERSAL_PREAMBLE_MAKO_DEFS = r"""//CL:mako//
                 );
         %endfor
 
-        ${name}_ext_center = 0.5*(${name}_min + ${name}_max);
-        ${name}_radii_vec = 0.5*(${name}_max - ${name}_min);
+        ${name}_ext_center = ((coord_vec_t) 0.5) * (${name}_min + ${name}_max);
+        ${name}_radii_vec = ((coord_vec_t) 0.5) * (${name}_max - ${name}_min);
     }
 </%def>
 
diff --git a/test/test_fmm.py b/test/test_fmm.py
index 082b43176d84385098d8298fd1f50e56c7383810..d9bbc398b3a37a9b4405879dc10ffa1a2e901e57 100644
--- a/test/test_fmm.py
+++ b/test/test_fmm.py
@@ -714,6 +714,59 @@ def test_interaction_list_particle_count_thresholding(ctx_getter, enable_extents
 # }}}
 
 
+# {{{ test fmm with float32 dtype
+
+@pytest.mark.parametrize("enable_extents", [True, False])
+def test_fmm_float32(ctx_getter, enable_extents):
+    ctx = ctx_getter()
+    queue = cl.CommandQueue(ctx)
+
+    logging.basicConfig(level=logging.INFO)
+
+    dims = 2
+    nsources = 1000
+    ntargets = 1000
+    dtype = np.float32
+
+    from boxtree.fmm import drive_fmm
+    sources = p_normal(queue, nsources, dims, dtype, seed=15)
+    targets = p_normal(queue, ntargets, dims, dtype, seed=15)
+
+    from pyopencl.clrandom import PhiloxGenerator
+    rng = PhiloxGenerator(queue.context, seed=12)
+
+    if enable_extents:
+        target_radii = 2**rng.uniform(queue, ntargets, dtype=dtype, a=-10, b=0)
+    else:
+        target_radii = None
+
+    from boxtree import TreeBuilder
+    tb = TreeBuilder(ctx)
+
+    tree, _ = tb(queue, sources, targets=targets,
+            max_particles_in_box=30,
+            target_radii=target_radii,
+            debug=True, stick_out_factor=0.25)
+
+    from boxtree.traversal import FMMTraversalBuilder
+    tbuild = FMMTraversalBuilder(ctx)
+    trav, _ = tbuild(queue, tree, debug=True)
+
+    weights = np.ones(nsources)
+    weights_sum = np.sum(weights)
+
+    host_trav = trav.get(queue=queue)
+    host_tree = host_trav.tree
+
+    wrangler = ConstantOneExpansionWrangler(host_tree)
+
+    pot = drive_fmm(host_trav, wrangler, weights)
+
+    assert (pot == weights_sum).all()
+
+# }}}
+
+
 # You can test individual routines by typing
 # $ python test_fmm.py 'test_routine(cl.create_some_context)'