diff --git a/src/nbmake/pytest_items.py b/src/nbmake/pytest_items.py
index ed69d9b..1ea5ffc 100644
--- a/src/nbmake/pytest_items.py
+++ b/src/nbmake/pytest_items.py
@@ -6,6 +6,7 @@
 import nbformat
 import pytest
 from _pytest._code.code import ReprFileLocation, TerminalRepr, TerminalWriter
+from nbformat.reader import NotJSONError
 from pygments import highlight
 from pygments.formatters import TerminalTrueColorFormatter
 from pygments.lexers import Python3TracebackLexer
@@ -75,7 +76,14 @@ def create_internal_err() -> Any:
                 "NBMAKE INTERNAL ERROR",
             )
 
-        if type(excinfo.value) != NotebookFailedException:
+        exc_type = type(excinfo.value)
+
+        if exc_type is NotJSONError:
+            return NbMakeFailureRepr(
+                "This file is not a valid json document", excinfo.value.args[0]
+            )
+
+        if exc_type != NotebookFailedException:
             return create_internal_err()
 
         res: NotebookResult = excinfo.value.args[0]
diff --git a/tests/test_pytest_plugin.py b/tests/test_pytest_plugin.py
index ad6f363..2749b47 100644
--- a/tests/test_pytest_plugin.py
+++ b/tests/test_pytest_plugin.py
@@ -195,3 +195,15 @@ def test_when_no_import_errs_then_pass(pytester: Pytester, testdir2: Never):
     hook_recorder = pytester.inline_run("--nbmake", "--nbmake-find-import-errors")
 
     assert hook_recorder.ret == ExitCode.OK
+
+
+def test_when_not_json_then_correct_err_msg(pytester: Pytester, testdir2: Never):
+
+    (Path(pytester.path) / "a.ipynb").write_text("invalid json")
+
+    hook_recorder = pytester.inline_run("--nbmake")
+
+    longrepr = hook_recorder.listoutcomes()[2][0].longrepr
+    assert longrepr is not None
+    assert "NBMAKE INTERNAL ERROR" not in longrepr.term
+    assert "json" in longrepr.term