diff --git a/src/zenml/utils/string_utils.py b/src/zenml/utils/string_utils.py
index 3cee230e1e2..f0d8519bc92 100644
--- a/src/zenml/utils/string_utils.py
+++ b/src/zenml/utils/string_utils.py
@@ -183,7 +183,7 @@ def format_name_template(
         KeyError: If a key in template is missing in the substitutions.
         ValueError: If the formatted name is empty.
     """
-    substitutions = substitutions or {}
+    substitutions = dict(substitutions or {})
 
     if ("date" not in substitutions and "{date}" in name_template) or (
         "time" not in substitutions and "{time}" in name_template
diff --git a/tests/unit/utils/test_string_utils.py b/tests/unit/utils/test_string_utils.py
index c2d715e63ac..861862f5555 100644
--- a/tests/unit/utils/test_string_utils.py
+++ b/tests/unit/utils/test_string_utils.py
@@ -116,3 +116,29 @@ def substitution_func(s):
         {3: "value_suffix", "key_suffix": model_sub},
         set(["set_value_suffix", 4]),
     ]
+
+
+def test_format_name_template_does_not_mutate_substitutions() -> None:
+    """The caller's substitutions dict must not be modified.
+
+    `substitutions or {}` only builds a new dict for a falsy argument, so a
+    non-empty dict was aliased and had date/time injected into it.
+    """
+    substitutions = {"custom": "value"}
+
+    formatted = string_utils.format_name_template(
+        "run-{custom}-{date}-{time}", substitutions=substitutions
+    )
+
+    assert substitutions == {"custom": "value"}
+    assert formatted.startswith("run-value-")
+
+
+def test_format_name_template_uses_given_substitutions() -> None:
+    """Explicit date/time substitutions are still honored."""
+    formatted = string_utils.format_name_template(
+        "run-{date}-{time}",
+        substitutions={"date": "2020_01_01", "time": "00_00_00"},
+    )
+
+    assert formatted == "run-2020_01_01-00_00_00"