diff --git a/grudge/models/wave.py b/grudge/models/wave.py
index ff8ee57e..7ac802b7 100644
--- a/grudge/models/wave.py
+++ b/grudge/models/wave.py
@@ -221,11 +221,11 @@ def __init__(self, dcoll, c, source_f=None,
 
         actx = c.array_context
         self.dcoll = dcoll
-        self.c = c
+        self.c = actx.freeze(c)
         self.source_f = source_f
 
-        ones = dcoll.zeros(actx) + 1
-        thawed_c = dcoll._setup_actx.thaw(c)
+        ones = dcoll.zeros(dcoll._setup_actx) + 1
+        thawed_c = dcoll._setup_actx.thaw(self.c)
         self.sign = dcoll._setup_actx.freeze(
                 actx.np.where(actx.np.greater(thawed_c, 0), ones, -ones))