diff --git a/src/crypto/rsa/rsa.go b/src/crypto/rsa/rsa.go
index 8a6014a..1293b78 100644
--- a/src/crypto/rsa/rsa.go
+++ b/src/crypto/rsa/rsa.go
@@ -146,6 +146,10 @@
 	// Check that Πprimes == n.
 	modulus := new(big.Int).Set(bigOne)
 	for _, prime := range priv.Primes {
+		// Any primes ≤ 1 will cause divide-by-zero panics later.
+		if prime.Cmp(bigOne) <= 0 {
+			return errors.New("crypto/rsa: invalid prime value")
+		}
 		modulus.Mul(modulus, prime)
 	}
 	if modulus.Cmp(priv.N) != 0 {
diff --git a/src/crypto/x509/x509_test.go b/src/crypto/x509/x509_test.go
index d83147b..f4f9fa2 100644
--- a/src/crypto/x509/x509_test.go
+++ b/src/crypto/x509/x509_test.go
@@ -41,6 +41,13 @@
 		priv.Primes[1].Cmp(rsaPrivateKey.Primes[1]) != 0 {
 		t.Errorf("got:%+v want:%+v", priv, rsaPrivateKey)
 	}
+
+	// This private key includes an invalid prime that
+	// rsa.PrivateKey.Validate should reject.
+	data := []byte("0\x16\x02\x00\x02\x02\u007f\x00\x02\x0200\x02\x0200\x02\x02\x00\x01\x02\x02\u007f\x00")
+	if _, err := ParsePKCS1PrivateKey(data); err == nil {
+		t.Errorf("parsing invalid private key did not result in an error")
+	}
 }
 
 func TestParsePKIXPublicKey(t *testing.T) {