diff --git a/loopy/__init__.py b/loopy/__init__.py
index 98db6200e3a3846343dcfe439712e763d54906af..272cde06719a8abddda121ef44acdec257d275ad 100644
--- a/loopy/__init__.py
+++ b/loopy/__init__.py
@@ -1253,7 +1253,7 @@ def register_preamble_generators(kernel, preamble_generators):
     new_pgens = kernel.preamble_generators[:]
     for pgen in preamble_generators:
         if pgen not in new_pgens:
-            new_pgens.append(pgen)
+            new_pgens.insert(0, pgen)
 
     return kernel.copy(preamble_generators=new_pgens)
 
@@ -1261,8 +1261,8 @@ def register_preamble_generators(kernel, preamble_generators):
 def register_symbol_manglers(kernel, manglers):
     new_manglers = kernel.symbol_manglers[:]
     for m in manglers:
-        if m not in manglers:
-            new_manglers.append(m)
+        if m not in new_manglers:
+            new_manglers.insert(0, m)
 
     return kernel.copy(symbol_manglers=new_manglers)
 
@@ -1270,8 +1270,8 @@ def register_symbol_manglers(kernel, manglers):
 def register_function_manglers(kernel, manglers):
     new_manglers = kernel.function_manglers[:]
     for m in manglers:
-        if m not in manglers:
-            new_manglers.append(m)
+        if m not in new_manglers:
+            new_manglers.insert(0, m)
 
     return kernel.copy(function_manglers=new_manglers)