diff --git a/tracetools_analysis/test/tracetools_analysis/test_dependency_solver.py b/tracetools_analysis/test/tracetools_analysis/test_dependency_solver.py
index 2bf86c0..7e33d0d 100644
--- a/tracetools_analysis/test/tracetools_analysis/test_dependency_solver.py
+++ b/tracetools_analysis/test/tracetools_analysis/test_dependency_solver.py
@@ -55,7 +55,7 @@ class TestDependencySolver(unittest.TestCase):
         depone_instance = DepOne()
 
         # DepEmtpy should be added before
-        solution = DependencySolver([depone_instance]).solve()
+        solution = DependencySolver(depone_instance).solve()
         self.assertEqual(len(solution), 2, 'solution length invalid')
         self.assertIsInstance(solution[0], DepEmtpy)
         self.assertIs(solution[1], depone_instance)
@@ -65,13 +65,13 @@ class TestDependencySolver(unittest.TestCase):
         depone_instance = DepOne()
 
         # Already in order
-        solution = DependencySolver([depempty_instance, depone_instance]).solve()
+        solution = DependencySolver(depempty_instance, depone_instance).solve()
         self.assertEqual(len(solution), 2, 'solution length invalid')
         self.assertIs(solution[0], depempty_instance, 'wrong solution order')
         self.assertIs(solution[1], depone_instance, 'wrong solution order')
 
         # Out of order
-        solution = DependencySolver([depone_instance, depempty_instance]).solve()
+        solution = DependencySolver(depone_instance, depempty_instance).solve()
         self.assertEqual(len(solution), 2, 'solution length invalid')
         self.assertIs(solution[0], depempty_instance, 'solution does not use existing instance')
         self.assertIs(solution[1], depone_instance, 'solution does not use existing instance')
@@ -80,7 +80,7 @@ class TestDependencySolver(unittest.TestCase):
         deptwo_instance = DepTwo()
 
         # DepOne and DepOne2 both depend on DepEmpty
-        solution = DependencySolver([deptwo_instance]).solve()
+        solution = DependencySolver(deptwo_instance).solve()
         self.assertEqual(len(solution), 4, 'solution length invalid')
         self.assertIsInstance(solution[0], DepEmtpy)
         self.assertIsInstance(solution[1], DepOne)
@@ -89,7 +89,7 @@ class TestDependencySolver(unittest.TestCase):
 
         # Existing instance of DepEmpty, in order
         depempty_instance = DepEmtpy()
-        solution = DependencySolver([depempty_instance, deptwo_instance]).solve()
+        solution = DependencySolver(depempty_instance, deptwo_instance).solve()
         self.assertEqual(len(solution), 4, 'solution length invalid')
         self.assertIsInstance(solution[0], DepEmtpy)
         self.assertIsInstance(solution[1], DepOne)
@@ -97,7 +97,7 @@ class TestDependencySolver(unittest.TestCase):
         self.assertIs(solution[3], deptwo_instance)
 
         # Existing instance of DepEmpty, not in order
-        solution = DependencySolver([deptwo_instance, depempty_instance]).solve()
+        solution = DependencySolver(deptwo_instance, depempty_instance).solve()
         self.assertEqual(len(solution), 4, 'solution length invalid')
         self.assertIsInstance(solution[0], DepEmtpy)
         self.assertIsInstance(solution[1], DepOne)
@@ -108,7 +108,7 @@ class TestDependencySolver(unittest.TestCase):
         depone_instance = DepOne()
 
         # Pass parameter and check that the new instance has it
-        solution = DependencySolver([depone_instance], myparam='myvalue').solve()
+        solution = DependencySolver(depone_instance, myparam='myvalue').solve()
         self.assertEqual(len(solution), 2, 'solution length invalid')
         self.assertEqual(solution[0].myparam, 'myvalue', 'parameter not passed on')
 
diff --git a/tracetools_analysis/tracetools_analysis/processor/__init__.py b/tracetools_analysis/tracetools_analysis/processor/__init__.py
index d38aa45..cf2dc1a 100644
--- a/tracetools_analysis/tracetools_analysis/processor/__init__.py
+++ b/tracetools_analysis/tracetools_analysis/processor/__init__.py
@@ -156,7 +156,7 @@ class DependencySolver():
 
     def __init__(
         self,
-        initial_dependants: List[Dependant],
+        *initial_dependants: Dependant,
         **kwargs,
     ) -> None:
         """
@@ -165,7 +165,7 @@ class DependencySolver():
         :param initial_dependants: the initial dependant instances, in order
         :param kwargs: the parameters to pass on to new instances
         """
-        self._initial_deps = initial_dependants
+        self._initial_deps = list(initial_dependants)
         self._kwargs = kwargs
 
     def solve(self) -> List[Dependant]:
@@ -241,10 +241,10 @@ class Processor():
         Constructor.
 
         :param handlers: the `EventHandler`s to use for processing
+        :param kwargs: the parameters to pass on to new handlers
         """
-        self._handlers = list(handlers)
-        print('handlers before:', [type(handler).__name__ for handler in self._handlers])
-        self._handlers = self._expand_dependencies(self._handlers, **kwargs)
+        print('handlers before:', [type(handler).__name__ for handler in handlers])
+        self._handlers = self._expand_dependencies(*handlers, **kwargs)
         print('handlers after:', [type(handler).__name__ for handler in self._handlers])
         self._register_with_handlers()
         input()
@@ -256,15 +256,16 @@ class Processor():
 
     def _expand_dependencies(
         self,
-        handlers: List[EventHandler],
+        *handlers: EventHandler,
         **kwargs,
     ) -> List[EventHandler]:
         """
         Check handlers and add dependencies if not included.
 
         :param handlers: the list of primary `EventHandler`s
+        :param kwargs: the parameters to pass on to new instances
         """
-        return DependencySolver(handlers, **kwargs).solve()
+        return DependencySolver(*handlers, **kwargs).solve()
 
     def _get_handler_maps(self) -> HandlerMultimap:
         """