diff --git a/pyop2/parloop.py b/pyop2/parloop.py
index 384576fa8..c70f4c9fb 100644
--- a/pyop2/parloop.py
+++ b/pyop2/parloop.py
@@ -121,7 +121,7 @@ def _kernel_args_(self):
     @property
     def map_kernel_args(self):
         rmap, cmap = self.maps
-        return tuple(itertools.chain(*itertools.product(rmap._kernel_args_, cmap._kernel_args_)))
+        return tuple(itertools.chain(rmap._kernel_args_, cmap._kernel_args_))
 
 
 @dataclass
@@ -143,7 +143,7 @@ def _kernel_args_(self):
     @property
     def map_kernel_args(self):
         rmap, cmap = self.maps
-        return tuple(itertools.chain(*itertools.product(rmap._kernel_args_, cmap._kernel_args_)))
+        return tuple(itertools.chain(rmap._kernel_args_, cmap._kernel_args_))
 
 
 @dataclass