diff --git a/src/aero_particle.hpp b/src/aero_particle.hpp
index 36c21759..14860302 100644
--- a/src/aero_particle.hpp
+++ b/src/aero_particle.hpp
@@ -222,7 +222,7 @@ struct AeroParticle {
     }
 
     static auto sources(const AeroParticle &self) {
-        int len = AeroData::__len__(*self.aero_data);
+        int len = AeroData::n_source(*self.aero_data);
         auto fn = f_aero_particle_get_component_sources;
         return pypartmc::get_array_values_set_len<int>(self, fn, len);
     }
diff --git a/tests/test_aero_particle.py b/tests/test_aero_particle.py
index 7c65cae6..372802dd 100644
--- a/tests/test_aero_particle.py
+++ b/tests/test_aero_particle.py
@@ -4,6 +4,7 @@
 # Authors: https://github.com/open-atmos/PyPartMC/graphs/contributors                              #
 ####################################################################################################
 
+import copy
 import gc
 
 import numpy as np
@@ -14,6 +15,7 @@
 
 from .test_aero_data import AERO_DATA_CTOR_ARG_MINIMAL
 from .test_aero_dist import AERO_DIST_CTOR_ARG_MINIMAL
+from .test_aero_mode import AERO_MODE_CTOR_LOG_NORMAL
 from .test_aero_state import AERO_STATE_CTOR_ARG_MINIMAL
 from .test_env_state import ENV_STATE_CTOR_ARG_MINIMAL
 
@@ -504,16 +506,23 @@ def test_refract_core():
     def test_sources():
         # arrange
         aero_data = ppmc.AeroData(AERO_DATA_CTOR_ARG_MINIMAL)
-        aero_dist = ppmc.AeroDist(aero_data, AERO_DIST_CTOR_ARG_MINIMAL)
+        # two log-normal modes differing only in name (i.e. source)
+        modes = copy.deepcopy(AERO_MODE_CTOR_LOG_NORMAL)
+        modes["test_mode_2"] = copy.deepcopy(AERO_MODE_CTOR_LOG_NORMAL["test_mode"])
+        aero_dist = ppmc.AeroDist(aero_data, [modes])
         aero_state = ppmc.AeroState(aero_data, *AERO_STATE_CTOR_ARG_MINIMAL)
         _ = aero_state.dist_sample(aero_dist, 1.0, 0.0)
-        sut = aero_state.particle(0)
+
         # act
-        sources = sut.sources
+        sources = [
+            aero_state.particle(i_part).sources for i_part in range(len(aero_state))
+        ]
 
         # assert
-        assert len(sources) == aero_dist.n_mode
-        assert isinstance(sources[0], int)
+        assert aero_data.n_source == aero_dist.n_mode
+        assert all(len(src) == aero_data.n_source for src in sources)
+        assert isinstance(sources[0][0], int)
+        assert all(sum(src) == 1 for src in sources)
 
     @staticmethod
     def test_get_weighting():