diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0a106a2..44a3e6a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,7 @@ All notable changes to this project are documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## 1.3.7, 2024-10-17
+## 1.3.6, 2024-10-17
 * Added: complete test framework, using pytest and Mkdocs-Test (#244)
   A number of automated test cases are implemented.
 * Changed: move from setup.py to pyproject.toml (#250)
diff --git a/mkdocs_macros/util.py b/mkdocs_macros/util.py
index 09f48dc..6796dfc 100644
--- a/mkdocs_macros/util.py
+++ b/mkdocs_macros/util.py
@@ -137,7 +137,11 @@ def default(self, obj: Any) -> Any:
             return super().default(obj)
         except TypeError:
             debug(f"json: cannot encode {obj.__class__}")
-            return str(obj)
+            try:
+                return str(obj)
+            except Exception:
+                # in case something happens along the line
+                return f"!Non printable object: {obj.__class__}"
 
 
 
diff --git a/pyproject.toml b/pyproject.toml
index 54ce588..5731e53 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -48,6 +48,7 @@ test = [
     "mkdocs-macros-test",
     "mkdocs-material>=6.2",
     "mkdocs-test",
+    "mkdocs-d2-plugin"
 ]
 
 [project.entry-points."mkdocs.plugins"]
diff --git a/test/plugin_d2/.cache/plugin/d2/db.db b/test/plugin_d2/.cache/plugin/d2/db.db
new file mode 100644
index 0000000..04f07d6
Binary files /dev/null and b/test/plugin_d2/.cache/plugin/d2/db.db differ
diff --git a/test/plugin_d2/__init__.py b/test/plugin_d2/__init__.py
new file mode 100644
index 0000000..7a6bb57
--- /dev/null
+++ b/test/plugin_d2/__init__.py
@@ -0,0 +1,4 @@
+"""
+This __init__.py file is indispensable for pytest to
+recognize its packages.
+"""
\ No newline at end of file
diff --git a/test/plugin_d2/docs/index.md b/test/plugin_d2/docs/index.md
new file mode 100644
index 0000000..ce5c57b
--- /dev/null
+++ b/test/plugin_d2/docs/index.md
@@ -0,0 +1,12 @@
+# Home
+
+This checks the compatibility with the d2 plugin.
+
+There used to be an issue, see [Github](https://github.com/fralau/mkdocs-macros-plugin/issues/249).
+
+It was due to the CustomEncoder class (in util module),
+which was susceptible to fail if an object was not printable.
+
+```d2
+A -> B
+```
diff --git a/test/plugin_d2/mkdocs.yaml b/test/plugin_d2/mkdocs.yaml
new file mode 100644
index 0000000..0cf7e00
--- /dev/null
+++ b/test/plugin_d2/mkdocs.yaml
@@ -0,0 +1,17 @@
+
+# Documentation name
+site_name: 'Compatibility with d2 plugin'
+
+# Your repository URL and name
+repo_url: https://gitlab.com/karreg/mkdocs-macros-d2-issue
+repo_name: mkdocs-macros-d2-issue
+
+# Plugins
+plugins:
+  - search
+  - d2
+  - macros
+
+# Documentation content
+nav:
+  - Home: 'index.md'
diff --git a/test/plugin_d2/test_t2.py b/test/plugin_d2/test_t2.py
new file mode 100644
index 0000000..d27f20f
--- /dev/null
+++ b/test/plugin_d2/test_t2.py
@@ -0,0 +1,43 @@
+"""
+Testing the d2 project
+
+There was an incompatibility:
+Error: The current file is not set for the '!relative' tag. It cannot be used in this context; the intended usage is within `markdown_extensions`.
+
+see https://github.com/fralau/mkdocs-macros-plugin/issues/249 
+
+Requires d2
+
+(C) Laurent Franceschetti 2024
+"""
+
+REQUIRED = "d2"
+
+import pytest
+import subprocess
+
+def is_d2_installed():
+    try:
+        subprocess.run(["brew", "list", REQUIRED], check=True, 
+                    stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+        return True
+    except subprocess.CalledProcessError:
+        return False
+
+
+import test
+from test.fixture import MacrosDocProject
+
+
+@pytest.mark.skipif(not is_d2_installed(), reason="d2 is not installed")
+def test_d2():
+    """
+    This test will run only if d2 library is installed;
+    otherwise the d2 plugin will not run
+    https://d2lang.com/tour/install/
+    """
+    project = MacrosDocProject()
+    project.build(strict=False)
+    # did not fail
+    print(project.build_result.stderr)
+    assert not project.build_result.returncode, "Failed when it should not" 
\ No newline at end of file