diff --git a/src/libsodium/crypto_stream/chacha20/ref/stream_chacha20_ref.c b/src/libsodium/crypto_stream/chacha20/ref/stream_chacha20_ref.c
index 0e0ef38c..5a64fd48 100644
--- a/src/libsodium/crypto_stream/chacha20/ref/stream_chacha20_ref.c
+++ b/src/libsodium/crypto_stream/chacha20/ref/stream_chacha20_ref.c
@@ -8,6 +8,7 @@
  */
 
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "api.h"
@@ -267,6 +268,9 @@ crypto_stream_chacha20_ietf_ref(unsigned char *c, unsigned long long clen,
     if (!clen) {
         return 0;
     }
+    if (clen > 64ULL * (1ULL << 32) - 64ULL) {
+        abort();
+    }
     (void) sizeof(int[crypto_stream_chacha20_KEYBYTES == 256 / 8 ? 1 : -1]);
     chacha_keysetup(&ctx, k);
     chacha_ietf_ivsetup(&ctx, n, NULL);