diff --git a/pendulum/__init__.py b/pendulum/__init__.py
index bb1e0ca7..b19f87d5 100644
--- a/pendulum/__init__.py
+++ b/pendulum/__init__.py
@@ -251,7 +251,10 @@ def yesterday(tz="local"):  # type: (Union[str, _Timezone]) -> DateTime
 
 
 def from_format(
-    string, fmt, tz=UTC, locale=None,  # noqa
+    string,
+    fmt,
+    tz=UTC,
+    locale=None,  # noqa
 ):  # type: (str, str, Union[str, _Timezone], Optional[str]) -> DateTime
     """
     Creates a DateTime instance from a specific format.
diff --git a/pendulum/parsing/__init__.py b/pendulum/parsing/__init__.py
index 1b5c8b91..57a5c010 100644
--- a/pendulum/parsing/__init__.py
+++ b/pendulum/parsing/__init__.py
@@ -212,7 +212,7 @@ def __init__(self, start=None, end=None, duration=None):
 
 
 def _parse_iso8601_interval(text):
-    if "/" not in text:
+    if text.count("/") != 1 or text.startswith("/") or text.endswith("/"):
         raise ParserError("Invalid interval")
 
     first, last = text.split("/")
diff --git a/tests/datetime/test_from_format.py b/tests/datetime/test_from_format.py
index 0949332c..398b68da 100644
--- a/tests/datetime/test_from_format.py
+++ b/tests/datetime/test_from_format.py
@@ -39,7 +39,8 @@ def test_from_format_with_timezone():
 def test_from_format_with_square_bracket_in_timezone():
     with pytest.raises(ValueError, match="^String does not match format"):
         pendulum.from_format(
-            "1975-05-21 22:32:11 Eu[rope/London", "YYYY-MM-DD HH:mm:ss z",
+            "1975-05-21 22:32:11 Eu[rope/London",
+            "YYYY-MM-DD HH:mm:ss z",
         )
 
 
diff --git a/tests/parsing/test_parsing.py b/tests/parsing/test_parsing.py
index bcd7a53e..9387667a 100644
--- a/tests/parsing/test_parsing.py
+++ b/tests/parsing/test_parsing.py
@@ -670,6 +670,18 @@ def test_invalid():
     with pytest.raises(ParserError):
         parse(text)
 
+    # Incomplete date
+    text = "/2020"
+
+    with pytest.raises(ParserError):
+        parse(text)
+
+    # Incomplete date
+    text = "2020/"
+
+    with pytest.raises(ParserError):
+        parse(text)
+
 
 def test_exif_edge_case():
     text = "2016:12:26 15:45:28"