diff --git a/django/core/validators.py b/django/core/validators.py
index 2092b52cd6..82e8db3e9c 100644
--- a/django/core/validators.py
+++ b/django/core/validators.py
@@ -97,7 +97,9 @@ class URLValidator(RegexValidator):
             self.schemes = schemes
 
     def __call__(self, value):
-        # Check first if the scheme is valid
+        if not isinstance(value, str):
+            raise ValidationError(self.message, code=self.code)
+        # Check if the scheme is valid.
         scheme = value.split('://')[0].lower()
         if scheme not in self.schemes:
             raise ValidationError(self.message, code=self.code)
diff --git a/tests/validators/tests.py b/tests/validators/tests.py
index baa744a9a6..5127bfecf5 100644
--- a/tests/validators/tests.py
+++ b/tests/validators/tests.py
@@ -222,6 +222,8 @@ TEST_DATA = [
     (URLValidator(EXTENDED_SCHEMES), 'git+ssh://git@github.com/example/hg-git.git', None),
 
     (URLValidator(EXTENDED_SCHEMES), 'git://-invalid.com', ValidationError),
+    (URLValidator(), None, ValidationError),
+    (URLValidator(), 56, ValidationError),
     (URLValidator(), 'no_scheme', ValidationError),
     # Trailing newlines not accepted
     (URLValidator(), 'http://www.djangoproject.com/\n', ValidationError),