diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index a2b0f3bf18..41f5c07ae9 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -491,6 +491,9 @@ def run_validators(self, value):
         errors = []
         for validator in self.validators:
             if hasattr(validator, 'set_context'):
+                # Need to make a copy, because validator instances often
+                # are initialised globally
+                validator = copy.deepcopy(validator)
                 validator.set_context(self)
 
             try: