diff --git a/lib/00_core/Pinc_Core.ml b/lib/00_core/Pinc_Core.ml
new file mode 100644
index 0000000..aace182
--- /dev/null
+++ b/lib/00_core/Pinc_Core.ml
@@ -0,0 +1,3 @@
+include StdlibExtension
+module StringMap = StringMap
+module StringSet = StringSet
diff --git a/lib/02_parsing/Utils.ml b/lib/00_core/StdlibExtension.ml
similarity index 100%
rename from lib/02_parsing/Utils.ml
rename to lib/00_core/StdlibExtension.ml
diff --git a/lib/00_core/StringSet.ml b/lib/00_core/StringSet.ml
new file mode 100644
index 0000000..9896b93
--- /dev/null
+++ b/lib/00_core/StringSet.ml
@@ -0,0 +1 @@
+include Set.Make (String)
diff --git a/lib/02_parsing/Transformer.ml b/lib/02_parsing/Transformer.ml
index f80aa2f..c2beb34 100644
--- a/lib/02_parsing/Transformer.ml
+++ b/lib/02_parsing/Transformer.ml
@@ -1,4 +1,3 @@
-open Utils
 open Ast
 
 type primitive_value =