diff --git a/devito/passes/iet/definitions.py b/devito/passes/iet/definitions.py
index e4195c95c6..0568e833ad 100644
--- a/devito/passes/iet/definitions.py
+++ b/devito/passes/iet/definitions.py
@@ -355,7 +355,9 @@ def place_definitions(self, iet, globs=None, **kwargs):
         includes = set()
         if isinstance(iet, EntryFunction) and globs:
             for i in sorted(globs, key=lambda f: f.name):
-                includes.add(self._alloc_array_on_global_mem(iet, i, storage))
+                v = self._alloc_array_on_global_mem(iet, i, storage)
+                if v:
+                    includes.add(v)
 
         iet, efuncs = self._inject_definitions(iet, storage)
 
diff --git a/devito/symbolics/extended_sympy.py b/devito/symbolics/extended_sympy.py
index 87a56c13b7..5db4f6b7d8 100644
--- a/devito/symbolics/extended_sympy.py
+++ b/devito/symbolics/extended_sympy.py
@@ -4,7 +4,7 @@
 
 import numpy as np
 import sympy
-from sympy import Expr, Integer, Function, Number, Tuple, sympify
+from sympy import Expr, Function, Number, Tuple, sympify
 from sympy.core.decorators import call_highest_priority
 
 from devito.tools import (Pickable, as_tuple, is_integer, float2, float3, float4,  # noqa
@@ -278,14 +278,10 @@ class ListInitializer(sympy.Expr, Pickable):
     def __new__(cls, params):
         args = []
         for p in as_tuple(params):
-            if isinstance(p, str):
-                args.append(Symbol(p))
-            elif is_integer(p):
-                args.append(Integer(p))
-            elif not isinstance(p, Expr):
-                raise ValueError("`params` must be an iterable of Expr or str")
-            else:
-                args.append(p)
+            try:
+                args.append(sympify(p))
+            except sympy.SympifyError:
+                raise ValueError("Illegal param `%s`" % p)
         obj = sympy.Expr.__new__(cls, *args)
         obj.params = tuple(args)
         return obj
diff --git a/tests/test_unexpansion.py b/tests/test_unexpansion.py
index 1e269328c1..8685e6626e 100644
--- a/tests/test_unexpansion.py
+++ b/tests/test_unexpansion.py
@@ -1,7 +1,8 @@
 import numpy as np
 
 from conftest import assert_structure, get_params, get_arrays, check_array
-from devito import Buffer, Eq, Function, TimeFunction, Grid, Operator, cos, sin
+from devito import (Buffer, Eq, Function, TimeFunction, Grid, Operator,
+                    Substitutions, Coefficient, cos, sin)
 from devito.types import Symbol
 
 
@@ -37,6 +38,15 @@ def test_fallback_to_default(self):
         op.arguments(dt=1, time_M=10)
         op.cfunction
 
+    def test_numeric_coeffs(self):
+        grid = Grid(shape=(11,), extent=(10.,))
+        u = Function(name='u', grid=grid, coefficients='symbolic', space_order=2)
+
+        coeffs = Substitutions(Coefficient(2, u, grid.dimensions[0], np.zeros(3)))
+
+        op = Operator(Eq(u, u.dx2, coefficients=coeffs), opt=({'expand': False},))
+        op.cfunction
+
 
 class Test1Pass(object):