diff --git a/crypto/curve25519/x25519_test.cc b/crypto/curve25519/x25519_test.cc
index 495741d027..99753ef87d 100644
--- a/crypto/curve25519/x25519_test.cc
+++ b/crypto/curve25519/x25519_test.cc
@@ -157,7 +157,9 @@ TEST(X25519Test, SmallOrder) {
 
 TEST(X25519Test, Iterated) {
   // Taken from https://tools.ietf.org/html/rfc7748#section-5.2.
-  uint8_t scalar[32] = {9}, point[32] = {9}, out[32];
+  uint8_t scalar[32] = {}, point[32] = {}, out[32];
+  scalar[0] = 9;
+  point[0] = 9;
 
   for (unsigned i = 0; i < 1000; i++) {
     EXPECT_TRUE(ctwrapX25519(out, scalar, point));
@@ -176,7 +178,9 @@ TEST(X25519Test, Iterated) {
 
 TEST(X25519Test, DISABLED_IteratedLarge) {
   // Taken from https://tools.ietf.org/html/rfc7748#section-5.2.
-  uint8_t scalar[32] = {9}, point[32] = {9}, out[32];
+  uint8_t scalar[32] = {}, point[32] = {}, out[32];
+  scalar[0] = 9;
+  point[0] = 9;
 
   for (unsigned i = 0; i < 1000000; i++) {
     EXPECT_TRUE(ctwrapX25519(out, scalar, point));