diff --git a/crypto/curve25519/curve25519.c b/crypto/curve25519/curve25519.c
index 3e805b88..14c94c83 100644
--- a/crypto/curve25519/curve25519.c
+++ b/crypto/curve25519/curve25519.c
@@ -231,7 +231,7 @@ static void fe_1(fe h) {
  *
  * Preconditions: b in {0,1}. */
 static void fe_cswap(fe f, fe g, unsigned int b) {
-  b = -b;
+  b = 0-b;
   unsigned i;
   for (i = 0; i < 10; i++) {
     int32_t x = f[i] ^ g[i];
@@ -807,7 +807,7 @@ static void fe_neg(fe h, const fe f) {
  *
  * Preconditions: b in {0,1}. */
 static void fe_cmov(fe f, const fe g, unsigned b) {
-  b = -b;
+  b = 0-b;
   unsigned i;
   for (i = 0; i < 10; i++) {
     int32_t x = f[i] ^ g[i];
diff --git a/tool/speed.cc b/tool/speed.cc
index e9584a13..54f3c75e 100644
--- a/tool/speed.cc
+++ b/tool/speed.cc
@@ -456,6 +456,8 @@ static bool Speed25519(const std::string &selected) {
         uint8_t out[32], in1[32], in2[32];
         memset(in1, 0, sizeof(in1));
         memset(in2, 0, sizeof(in2));
+        in1[0] = 1;
+        in2[0] = 9;
         return X25519(out, in1, in2) == 1;
       })) {
     fprintf(stderr, "Curve25519 arbitrary point multiplication failed.\n");