diff --git a/python/dune/perftool/loopy/target.py b/python/dune/perftool/loopy/target.py
index 9a00a87662f563b4f034a4cb3cd72996fea68af7..5afce14911ed699b507a66490afe13e785680403 100644
--- a/python/dune/perftool/loopy/target.py
+++ b/python/dune/perftool/loopy/target.py
@@ -9,6 +9,7 @@ from dune.perftool.generation import (include_file,
                                       retrieve_cache_functions,
                                       )
 from dune.perftool.options import get_option
+from dune.perftool.tools import round_to_multiple
 
 from loopy.symbolic import Literal
 from loopy.target import (TargetBase,
@@ -197,6 +198,7 @@ class DuneASTBuilder(CASTBuilder):
 
             alignment = max(alignment)
             size = max(size)
+            size = round_to_multiple(size, alignment)
 
             decl =  "char {}[{}] __attribute__ ((aligned({})));".format(bs, size * 8, alignment)
             ret.append(cgen.Line(decl))