diff --git a/pystencils/rng.py b/pystencils/rng.py
index afc08b033ee23983966fd2ce09c99a8d28580f58..26a92b313de13343c02375f6bfb003fca15b418f 100644
--- a/pystencils/rng.py
+++ b/pystencils/rng.py
@@ -26,13 +26,12 @@ class PhiloxTwoDoubles(CustomCodeNode):
 
     def __init__(self, dim, time_step=TypedSymbol("time_step", np.uint32), keys=(0, 0)):
         self.result_symbols = tuple(TypedSymbol(sp.Dummy().name, np.float64) for _ in range(2))
-
         symbols_read = [s for s in keys if isinstance(s, sp.Symbol)]
         super().__init__("", symbols_read=symbols_read, symbols_defined=self.result_symbols)
         self._time_step = time_step
         self.headers = ['"philox_rand.h"']
-        self.keys = list(keys)
-        self._args = (time_step, *sp.sympify(keys))
+        self.keys = tuple(keys)
+        self._args = sp.sympify((dim, time_step, keys))
         self._dim = dim
 
     @property
@@ -47,9 +46,12 @@ class PhiloxTwoDoubles(CustomCodeNode):
         result.update(loop_counters)
         return result
 
+    def fast_subs(self, _):
+        return self  # nothing to replace inside this node - would destroy intermediate "dummy" by re-creating them
+
     def get_code(self, dialect, vector_instruction_set):
         parameters = [self._time_step] + [LoopOverCoordinate.get_loop_counter_symbol(i)
-                                          for i in range(self._dim)] + self.keys
+                                          for i in range(self._dim)] + list(self.keys)
 
         while len(parameters) < 6:
             parameters.append(0)
@@ -76,8 +78,8 @@ class PhiloxFourFloats(CustomCodeNode):
         super().__init__("", symbols_read=symbols_read, symbols_defined=self.result_symbols)
         self._time_step = time_step
         self.headers = ['"philox_rand.h"']
-        self.keys = list(keys)
-        self._args = (time_step, *sp.sympify(keys))
+        self.keys = tuple(keys)
+        self._args = sp.sympify((dim, time_step, keys))
         self._dim = dim
 
     @property
@@ -92,9 +94,12 @@ class PhiloxFourFloats(CustomCodeNode):
         result.update(loop_counters)
         return result
 
+    def fast_subs(self, _):
+        return self  # nothing to replace inside this node - would destroy intermediate "dummy" by re-creating them
+
     def get_code(self, dialect, vector_instruction_set):
         parameters = [self._time_step] + [LoopOverCoordinate.get_loop_counter_symbol(i)
-                                          for i in range(self._dim)] + self.keys
+                                          for i in range(self._dim)] + list(self.keys)
 
         while len(parameters) < 6:
             parameters.append(0)