diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d6066030f5e22234c82fb5bfaefa9bae004a8a8e..80f38616e1abbe4e560d9bbfbd2542d02bfe5007 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -139,7 +139,7 @@ unittest_py37:
   stage: unittest
   image: python:3.7
   script: &python_test_script
-    - pip install nose pandas pytest pytest-cov gitignore-parser openpyxl>=3.0.7 xlrd==1.2 h5py jsonref
+    - pip install nose pandas pytest pytest-cov gitignore-parser openpyxl>=3.0.7 xlrd==1.2 h5py
     - pip install git+https://gitlab.indiscale.com/caosdb/src/caosdb-pylib.git@dev
     - pip install .
     - pytest --cov=caosadvancedtools unittests
diff --git a/setup.py b/setup.py
index eed060aaf515260a03c1cbde6d205a8fa06ae395..4f4d8943fa16b842dfe3d25f3d83bc76b64e42b8 100755
--- a/setup.py
+++ b/setup.py
@@ -156,6 +156,7 @@ def setup_package():
         author_email='h.tomwoerden@indiscale.com',
         python_requires='>=3.7',
         install_requires=["caosdb>=0.11.0",
+                          "jsonref",
                           "jsonschema>=4.4.0",
                           "numpy>=1.17.3",
                           "openpyxl>=3.0.7",
@@ -164,7 +165,6 @@ def setup_package():
                           ],
         extras_require={"h5-crawler": ["h5py>=3.3.0", ],
                         "gitignore-parser": ["gitignore-parser >=0.1.0", ],
-                        "jsonref": ["jsonref", ],
                         },
         packages=find_packages('src'),
         package_dir={'': 'src'},
diff --git a/src/caosadvancedtools/models/parser.py b/src/caosadvancedtools/models/parser.py
index abf47d03c056714a66295aefefc3800f1d3dfd7a..a0da3b24cadced579dc9b124f8ef30c86e880f4f 100644
--- a/src/caosadvancedtools/models/parser.py
+++ b/src/caosadvancedtools/models/parser.py
@@ -747,6 +747,11 @@ class JsonSchemaParser(Parser):
                     "be identified with CaosDB's name property."
                 )
             return None, force_list
+        # LinkAhead suports null for all types, so in the very special case of
+        # `"type": ["null", "<other_type>"]`, only consider the other type:
+        if isinstance(elt["type"], list) and len(elt["type"]) == 2 and "null" in elt["type"]:
+            elt["type"].remove("null")
+            elt["type"] = elt["type"][0]
         if "enum" in elt:
             ent = self._treat_enum(elt, name)
         elif elt["type"] in JSON_SCHEMA_ATOMIC_TYPES:
diff --git a/tox.ini b/tox.ini
index ce18fc00b3eac352ac3b5c4fdd4d580961f7b6ee..0e9664c377366923b60e11d138825e1543cc8c7f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -12,7 +12,6 @@ deps=nose
     openpyxl >= 3.0.7
     xlrd == 1.2
     h5py
-    jsonref
 commands=py.test --cov=caosadvancedtools -vv {posargs}
 
 [flake8]