diff --git a/include/openmc/capi.h b/include/openmc/capi.h
index 5e74446f1..617153b6c 100644
--- a/include/openmc/capi.h
+++ b/include/openmc/capi.h
@@ -71,7 +71,7 @@ extern "C" {
   int openmc_nuclide_name(int index, const char** name);
   int openmc_plot_geometry();
   int openmc_id_map(const void* slice, int32_t *data_out);
-  int openmc_property_map(void* slice, double *data_out);
+  int openmc_property_map(const void* slice, double *data_out);
   int openmc_reset();
   int openmc_run();
   void openmc_set_seed(int64_t new_seed);
diff --git a/openmc/capi/plot.py b/openmc/capi/plot.py
index e8d1c06b4..c950f278b 100644
--- a/openmc/capi/plot.py
+++ b/openmc/capi/plot.py
@@ -236,7 +236,7 @@ def property_map(plot):
              of OpenMC property ids with dtype float
 
     """
-    prop_data = np.zeros((plot.vRes, plot.hRes, 2),
+    prop_data = np.zeros((plot.v_res, plot.h_res, 2),
                          dtype=np.dtype('float'))
     _dll.openmc_property_map(POINTER(_PlotBase)(plot),
                              prop_data.ctypes.data_as(POINTER(c_double)))
diff --git a/src/plot.cpp b/src/plot.cpp
index 5a35ceb40..45782b802 100644
--- a/src/plot.cpp
+++ b/src/plot.cpp
@@ -1075,19 +1075,18 @@ extern "C" int openmc_id_map(const void* plot, int32_t* data_out)
   return 0;
 }
 
-extern "C" int openmc_property_map(void* plot, double* data_out) {
+extern "C" int openmc_property_map(const void* plot, double* data_out) {
 
-  auto plt = reinterpret_cast<PlotBase*>(plot);
+  auto plt = reinterpret_cast<const PlotBase*>(plot);
   if (!plt) {
     set_errmsg("Invalid slice pointer passed to openmc_id_map");
     return OPENMC_E_INVALID_ARGUMENT;
   }
 
-  PropertyData data = plt->get_property_map();
+  PropertyData props = plt->get_property_map();
 
   // write id data to array
-  size_t i = 0;
-  for (auto v : data) { data_out[i++] = v; }
+  std::copy(props.begin(), props.end(), data_out);
 
   return 0;
 }
diff --git a/tests/unit_tests/test_capi.py b/tests/unit_tests/test_capi.py
index 1d2fb2ecb..14dac21fc 100644
--- a/tests/unit_tests/test_capi.py
+++ b/tests/unit_tests/test_capi.py
@@ -430,13 +430,11 @@ def test_property_map(capi_init):
     s = openmc.capi.plot._PlotBase()
     s.width = 1.26
     s.height = 1.26
-    s.vRes = 3
-    s.hRes = 3
+    s.v_res = 3
+    s.h_res = 3
     s.origin = (0.0, 0.0, 0.0)
     s.basis = 'xy'
     s.level = -1
 
     properties = openmc.capi.plot.property_map(s)
-    print(properties)
-    print(expected_properties)
     assert np.allclose(expected_properties, properties, atol=1e-04)