diff --git a/src/libsodium/include/sodium/private/common.h b/src/libsodium/include/sodium/private/common.h
index f5e5d7e7..9d9df3ea 100644
--- a/src/libsodium/include/sodium/private/common.h
+++ b/src/libsodium/include/sodium/private/common.h
@@ -5,6 +5,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+#define COMPILER_ASSERT(X) (void) sizeof(char[(X) ? 1 : -1])
+
 #define LOAD64_LE(SRC) load64_le(SRC)
 static inline uint64_t
 load64_le(const uint8_t src[8])
diff --git a/src/libsodium/include/sodium/randombytes.h b/src/libsodium/include/sodium/randombytes.h
index edec3f5f..05f5f365 100644
--- a/src/libsodium/include/sodium/randombytes.h
+++ b/src/libsodium/include/sodium/randombytes.h
@@ -25,9 +25,17 @@ typedef struct randombytes_implementation {
     int         (*close)(void);               /* optional */
 } randombytes_implementation;
 
+#define randombytes_SEEDBYTES 32U
+SODIUM_EXPORT
+size_t randombytes_seedbytes(void);
+
 SODIUM_EXPORT
 void randombytes_buf(void * const buf, const size_t size);
 
+SODIUM_EXPORT
+void randombytes_buf_deterministic(void * const buf, const size_t size,
+                                   const unsigned char seed[randombytes_SEEDBYTES]);
+
 SODIUM_EXPORT
 uint32_t randombytes_random(void);
 
diff --git a/src/libsodium/randombytes/randombytes.c b/src/libsodium/randombytes/randombytes.c
index 6c3fb2bd..56612c67 100644
--- a/src/libsodium/randombytes/randombytes.c
+++ b/src/libsodium/randombytes/randombytes.c
@@ -10,6 +10,7 @@
 # include <emscripten.h>
 #endif
 
+#include "crypto_stream_chacha20.h"
 #include "randombytes.h"
 #ifdef RANDOMBYTES_DEFAULT_IMPLEMENTATION
 # include "randombytes_default.h"
@@ -20,6 +21,7 @@
 #  include "randombytes_sysrandom.h"
 # endif
 #endif
+#include "private/common.h"
 
 /* C++Builder defines a "random" macro */
 #undef random
@@ -163,6 +165,22 @@ randombytes_buf(void * const buf, const size_t size)
 #endif
 }
 
+void
+randombytes_buf_deterministic(void * const buf, const size_t size,
+                              const unsigned char seed[randombytes_SEEDBYTES])
+{
+    static const unsigned char zero[crypto_stream_chacha20_NONCEBYTES];
+
+    COMPILER_ASSERT(randombytes_SEEDBYTES == crypto_stream_chacha20_KEYBYTES);
+    crypto_stream_chacha20((unsigned char *) buf, size, zero, seed);
+}
+
+size_t
+randombytes_seedbytes(void)
+{
+    return randombytes_SEEDBYTES;
+}
+
 int
 randombytes_close(void)
 {
diff --git a/src/libsodium/randombytes/salsa20/randombytes_salsa20_random.c b/src/libsodium/randombytes/salsa20/randombytes_salsa20_random.c
index 66969d39..78f3b5e1 100644
--- a/src/libsodium/randombytes/salsa20/randombytes_salsa20_random.c
+++ b/src/libsodium/randombytes/salsa20/randombytes_salsa20_random.c
@@ -31,6 +31,7 @@
 #include "randombytes.h"
 #include "randombytes_salsa20_random.h"
 #include "utils.h"
+#include "private/common.h"
 
 #ifdef _WIN32
 # include <windows.h>
@@ -49,7 +50,6 @@ BOOLEAN NTAPI RtlGenRandom(PVOID RandomBuffer, ULONG RandomBufferLength);
 
 #define SALSA20_RANDOM_BLOCK_SIZE crypto_core_salsa20_OUTPUTBYTES
 #define HASH_BLOCK_SIZE 128U
-#define COMPILER_ASSERT(X) (void) sizeof(char[(X) ? 1 : -1])
 
 #if defined(__OpenBSD__) || defined(__CloudABI__)
 # define HAVE_SAFE_ARC4RANDOM 1
diff --git a/test/default/randombytes.c b/test/default/randombytes.c
index 80c560de..77319d03 100644
--- a/test/default/randombytes.c
+++ b/test/default/randombytes.c
@@ -27,9 +27,16 @@ static int compat_tests(void)
 
 static int randombytes_tests(void)
 {
-    unsigned int f = 0U;
-    unsigned int i;
-    uint32_t     n;
+    const static unsigned char seed[randombytes_SEEDBYTES] = {
+        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+        0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+        0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+        0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f
+    };
+    unsigned char out[100];
+    unsigned int  f = 0U;
+    unsigned int  i;
+    uint32_t      n;
 
 #ifdef __EMSCRIPTEN__
     assert(strcmp(randombytes_implementation_name(), "js") == 0);
@@ -92,6 +99,13 @@ static int randombytes_tests(void)
         }
     }
     assert(randombytes_uniform(1U) == 0U);
+
+    randombytes_buf_deterministic(out, sizeof out, seed);
+    for (i = 0; i < sizeof out; ++i) {
+        printf("%02x", out[i]);
+    }
+    printf(" (deterministic)\n");
+
     randombytes_close();
 
     randombytes(x, 1U);
diff --git a/test/default/randombytes.exp b/test/default/randombytes.exp
index d86bac9d..db789bf8 100644
--- a/test/default/randombytes.exp
+++ b/test/default/randombytes.exp
@@ -1 +1,2 @@
+39fd2b7dd9c5196a8dbd0377b8dc4a498a35d86fbcde6accb2cc7d4cd8ea24922b23cce7a26023ab3f0eef693ac87f64258235eab1f7a32dc22762a0485b410c18b84231ade6a6d113615c61af434e27f8b1f3f5e1ad5b5cecf8fc122a35755c7208086d (deterministic)
 OK