diff --git a/src/cryptography/hazmat/primitives/asymmetric/ec.py b/src/cryptography/hazmat/primitives/asymmetric/ec.py
index 023a2d1..a527387 100644
--- a/src/cryptography/hazmat/primitives/asymmetric/ec.py
+++ b/src/cryptography/hazmat/primitives/asymmetric/ec.py
@@ -257,6 +257,9 @@
     if not isinstance(private_value, six.integer_types):
         raise TypeError("private_value must be an integer type.")
 
+    if private_value <= 0:
+        raise ValueError("private_value must be a positive integer.")
+
     if not isinstance(curve, EllipticCurve):
         raise TypeError("curve must provide the EllipticCurve interface.")
 
diff --git a/tests/hazmat/primitives/test_ec.py b/tests/hazmat/primitives/test_ec.py
index d2b570d..7127071 100644
--- a/tests/hazmat/primitives/test_ec.py
+++ b/tests/hazmat/primitives/test_ec.py
@@ -125,6 +125,9 @@
     with pytest.raises(TypeError):
         ec.derive_private_key(10, 'five', backend)
 
+    with pytest.raises(ValueError):
+        ec.derive_private_key(-7, curve, backend)
+
 
 def test_ec_numbers():
     numbers = ec.EllipticCurvePrivateNumbers(