diff --git a/src/test/keyctl.c b/src/test/keyctl.c
index 63e7559c463..1b488a95558 100644
--- a/src/test/keyctl.c
+++ b/src/test/keyctl.c
@@ -13,7 +13,7 @@ struct rr_keyctl_dh_params {
 };
 
 int main(void) {
-  char buffer[192];
+  char buffer[256];
 
   char* data = "Test Data";
   key_serial_t key = syscall(SYS_add_key, "user", "RR Test key", data,
@@ -35,9 +35,9 @@ int main(void) {
   test_assert(0 == syscall(SYS_keyctl, KEYCTL_INVALIDATE, key));
 
 #ifdef KEYCTL_DH_COMPUTE
-  uint8_t base[192] = { 1 };
+  uint8_t base[256] = { 1 };
   // 'prime' must be at least 1536 bits or we get EINVAL.
-  uint8_t prime[192] = { 7 }; // Not prime but we should be OK
+  uint8_t prime[256] = { 7 }; // Not prime but we should be OK
   uint8_t private = 1;        // The world's worst private key
   base[191] = 'x';