diff --git a/src/crypto/dsa/dsa.go b/src/crypto/dsa/dsa.go
index 96768ce2a0..e9b6a0c253 100644
--- a/src/crypto/dsa/dsa.go
+++ b/src/crypto/dsa/dsa.go
@@ -247,6 +247,10 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err err
 func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool {
 	// FIPS 186-3, section 4.7
 
+	if pub.P.Sign() == 0 {
+		return false
+	}
+
 	if r.Sign() < 1 || r.Cmp(pub.Q) >= 0 {
 		return false
 	}