diff --git a/include/openmc.h b/include/openmc.h
index a9ffa74d75..2c0f10eae0 100644
--- a/include/openmc.h
+++ b/include/openmc.h
@@ -32,7 +32,7 @@ extern "C" {
   int openmc_extend_sources(int32_t n, int32_t* index_start, int32_t* index_end);
   int openmc_extend_tallies(int32_t n, int32_t* index_start, int32_t* index_end);
   int openmc_filter_get_id(int32_t index, int32_t* id);
-  int openmc_filter_get_type(int32_t index, const char* type);
+  int openmc_filter_get_type(int32_t index, char* type);
   int openmc_filter_set_id(int32_t index, int32_t id);
   int openmc_filter_set_type(int32_t index, const char* type);
   int openmc_finalize();
diff --git a/openmc/capi/filter.py b/openmc/capi/filter.py
index 611efb7fda..391e63f073 100644
--- a/openmc/capi/filter.py
+++ b/openmc/capi/filter.py
@@ -209,6 +209,11 @@ class EnergyFunctionFilter(Filter):
 class LegendreFilter(Filter):
     filter_type = 'legendre'
 
+    def __init__(self, order=None, uid=None, new=True, index=None):
+        super().__init__(uid, new, index)
+        if order is not None:
+            self.order = order
+
     @property
     def order(self):
         temp_order = c_int()
@@ -293,6 +298,11 @@ class PolarFilter(Filter):
 class SphericalHarmonicsFilter(Filter):
     filter_type = 'sphericalharmonics'
 
+    def __init__(self, order=None, uid=None, new=True, index=None):
+        super().__init__(uid, new, index)
+        if order is not None:
+            self.order = order
+
     @property
     def order(self):
         temp_order = c_int()
@@ -307,6 +317,11 @@ class SphericalHarmonicsFilter(Filter):
 class SpatialLegendreFilter(Filter):
     filter_type = 'spatiallegendre'
 
+    def __init__(self, order=None, uid=None, new=True, index=None):
+        super().__init__(uid, new, index)
+        if order is not None:
+            self.order = order
+
     @property
     def order(self):
         temp_order = c_int()
@@ -329,6 +344,11 @@ class UniverseFilter(Filter):
 class ZernikeFilter(Filter):
     filter_type = 'zernike'
 
+    def __init__(self, order=None, uid=None, new=True, index=None):
+        super().__init__(uid, new, index)
+        if order is not None:
+            self.order = order
+
     @property
     def order(self):
         temp_order = c_int()
diff --git a/tests/unit_tests/test_capi.py b/tests/unit_tests/test_capi.py
index 11a47b1506..af013cbb5b 100644
--- a/tests/unit_tests/test_capi.py
+++ b/tests/unit_tests/test_capi.py
@@ -205,7 +205,8 @@ def test_tally_results(capi_run):
     assert np.all(t.ci_width()[nonzero] >= 1.95*t.std_dev[nonzero])
 
     t2 = openmc.capi.tallies[2]
-    assert t2.mean.size == 63 # 21 coefficients for 5th order Zernike * 3 cells
+    n = 5
+    assert t2.mean.size == (n + 1) * (n + 2) // 2 * 3 # Number of Zernike coeffs * 3 cells
 
 
 def test_global_tallies(capi_run):