diff --git a/aligned/compiler/transformation_factory.py b/aligned/compiler/transformation_factory.py
index 12f26e3..9378954 100644
--- a/aligned/compiler/transformation_factory.py
+++ b/aligned/compiler/transformation_factory.py
@@ -387,7 +387,8 @@ def using_features(self) -> list[FeatureFactory]:
     def compile(self) -> Transformation:
         from aligned.schemas.transformation import ReplaceStrings
 
-        return ReplaceStrings(self.source_feature.name, self.values)
+        values = list(self.values.items())
+        return ReplaceStrings(self.source_feature.name, values)
 
 
 @dataclass
diff --git a/aligned/schemas/feature.py b/aligned/schemas/feature.py
index d331913..1d8b613 100644
--- a/aligned/schemas/feature.py
+++ b/aligned/schemas/feature.py
@@ -23,6 +23,7 @@
     'uuid': pl.Utf8,
     'array': pl.List(pl.Utf8),
     'embedding': pl.List,
+    'json': pl.Utf8,
 }
 
 
diff --git a/pyproject.toml b/pyproject.toml
index b24e4be..b8caf0e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "aligned"
-version = "0.0.57"
+version = "0.0.58"
 description = "A data managment and lineage tool for ML applications."
 authors = ["Mats E. Mollestad <mats@mollestad.no>"]
 license = "Apache-2.0"