diff --git a/check_source/check_spelling_c_config.py b/check_source/check_spelling_c_config.py
index b5203c62ec602d493693342be55dd8fc774a94ed..2964d5eccebe01747cc4a74940460e1bf492372e 100644
--- a/check_source/check_spelling_c_config.py
+++ b/check_source/check_spelling_c_config.py
@@ -177,6 +177,7 @@ dict_custom = {
     "overridable",
     "paddings",
     "pannable",
+    "parallelepiped",
     "parallelize",
     "parallelizing",
     "parameterization",
@@ -272,6 +273,7 @@ dict_custom = {
     "subclassing",
     "subdirectories",
     "subdirectory",
+    "suboptimally",
     "subtractive",
     "superset",
     "symmetrize",