diff --git a/docs/changelog/2665.bugfix.rst b/docs/changelog/2665.bugfix.rst
new file mode 100644
index 000000000..a4be5e9df
--- /dev/null
+++ b/docs/changelog/2665.bugfix.rst
@@ -0,0 +1 @@
+Use ``!r`` and ``repr()`` to better display erroneous values in exception from ``StrConverter.to_bool()`` - by :user:`ptmcg`.
diff --git a/src/tox/config/loader/str_convert.py b/src/tox/config/loader/str_convert.py
index dd518e5e3..e31c034f0 100644
--- a/src/tox/config/loader/str_convert.py
+++ b/src/tox/config/loader/str_convert.py
@@ -81,13 +81,15 @@ def to_env_list(value: str) -> EnvList:
 
     @staticmethod
     def to_bool(value: str) -> bool:
-        norm = value.strip().lower()
+        norm = str(value).strip().lower()
         if norm in StrConvert.TRUTHFUL_VALUES:
             return True
         elif norm in StrConvert.FALSE_VALUES:
             return False
         else:
-            raise TypeError(f"value {value} cannot be transformed to bool, valid: {', '.join(StrConvert.VALID_BOOL)}")
+            raise TypeError(
+                f"value {value!r} cannot be transformed to bool, valid: {', '.join(StrConvert.VALID_BOOL)}",
+            )
 
 
 __all__ = ("StrConvert",)
diff --git a/tests/config/test_sets.py b/tests/config/test_sets.py
index ca5778754..0faa68acd 100644
--- a/tests/config/test_sets.py
+++ b/tests/config/test_sets.py
@@ -89,7 +89,7 @@ def test_config_bad_bool(conf_builder: ConfBuilder) -> None:
     config_set.add_config(keys="bad_bool", of_type=bool, default=False, desc="bad_bool")
     with pytest.raises(TypeError) as context:
         assert config_set["bad_bool"]
-    error = "value whatever cannot be transformed to bool, valid: , 0, 1, false, no, off, on, true, yes"
+    error = "value 'whatever' cannot be transformed to bool, valid: , 0, 1, false, no, off, on, true, yes"
     assert str(context.value) == error