diff --git a/pyproject.toml b/pyproject.toml
index a09614e2..32a9c27e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "roc-validator"
-version = "0.4.1"
+version = "0.4.2"
 description = "A Python package to validate RO-Crates"
 authors = [
     "Marco Enrico Piras <kikkomep@crs4.it>",
diff --git a/rocrate_validator/constants.py b/rocrate_validator/constants.py
index 0051afe8..83b39d79 100644
--- a/rocrate_validator/constants.py
+++ b/rocrate_validator/constants.py
@@ -82,3 +82,6 @@
     'MAY', 'OPTIONAL', 'SHOULD', 'SHOULD_NOT',
     'REQUIRED', 'MUST', 'MUST_NOT', 'SHALL', 'SHALL_NOT', 'RECOMMENDED'
 ]
+
+# Current JSON output format
+JSON_OUTPUT_FORMAT_VERSION = "0.1"
diff --git a/rocrate_validator/models.py b/rocrate_validator/models.py
index 12bfcf3b..74714a92 100644
--- a/rocrate_validator/models.py
+++ b/rocrate_validator/models.py
@@ -33,7 +33,8 @@
 from rocrate_validator.constants import (DEFAULT_ONTOLOGY_FILE,
                                          DEFAULT_PROFILE_IDENTIFIER,
                                          DEFAULT_PROFILE_README_FILE,
-                                         IGNORED_PROFILE_DIRECTORIES, PROF_NS,
+                                         IGNORED_PROFILE_DIRECTORIES,
+                                         JSON_OUTPUT_FORMAT_VERSION, PROF_NS,
                                          PROFILE_FILE_EXTENSIONS,
                                          PROFILE_SPECIFICATION_FILE,
                                          RDF_SERIALIZATION_FORMATS_TYPES,