diff --git a/src/libsodium/crypto_onetimeauth/poly1305/53/auth_poly1305_53.c b/src/libsodium/crypto_onetimeauth/poly1305/53/auth_poly1305_53.c
index fccfc9d0..eebbc71b 100644
--- a/src/libsodium/crypto_onetimeauth/poly1305/53/auth_poly1305_53.c
+++ b/src/libsodium/crypto_onetimeauth/poly1305/53/auth_poly1305_53.c
@@ -10,6 +10,7 @@ Public domain.
 
 #include "api.h"
 #include "crypto_onetimeauth_poly1305_53.h"
+#include "utils.h"
 
 #pragma STDC FENV_ACCESS ON
 
@@ -1641,7 +1642,7 @@ crypto_onetimeauth_poly1305_implementation_name(void)
 
 struct crypto_onetimeauth_poly1305_implementation
 crypto_onetimeauth_poly1305_53_implementation = {
-    .implementation_name = crypto_onetimeauth_poly1305_implementation_name,
-    .onetimeauth = crypto_onetimeauth,
-    .onetimeauth_verify = crypto_onetimeauth_verify
+    _SODIUM_C99(.implementation_name =) crypto_onetimeauth_poly1305_implementation_name,
+    _SODIUM_C99(.onetimeauth =) crypto_onetimeauth,
+    _SODIUM_C99(.onetimeauth_verify =) crypto_onetimeauth_verify
 };
diff --git a/src/libsodium/crypto_onetimeauth/poly1305/ref/auth_poly1305_ref.c b/src/libsodium/crypto_onetimeauth/poly1305/ref/auth_poly1305_ref.c
index 43aa811e..9c4219eb 100644
--- a/src/libsodium/crypto_onetimeauth/poly1305/ref/auth_poly1305_ref.c
+++ b/src/libsodium/crypto_onetimeauth/poly1305/ref/auth_poly1305_ref.c
@@ -6,6 +6,7 @@ Public domain.
 
 #include "api.h"
 #include "crypto_onetimeauth_poly1305_ref.h"
+#include "utils.h"
 
 static void add(unsigned int h[17],const unsigned int c[17])
 {
@@ -112,7 +113,7 @@ crypto_onetimeauth_poly1305_implementation_name(void)
 
 struct crypto_onetimeauth_poly1305_implementation
 crypto_onetimeauth_poly1305_ref_implementation = {
-    .implementation_name = crypto_onetimeauth_poly1305_implementation_name,
-    .onetimeauth = crypto_onetimeauth,
-    .onetimeauth_verify = crypto_onetimeauth_verify
+    _SODIUM_C99(.implementation_name =) crypto_onetimeauth_poly1305_implementation_name,
+    _SODIUM_C99(.onetimeauth =) crypto_onetimeauth,
+    _SODIUM_C99(.onetimeauth_verify =) crypto_onetimeauth_verify
 };
diff --git a/src/libsodium/include/sodium/utils.h b/src/libsodium/include/sodium/utils.h
index 149a5cdf..7e3778dc 100644
--- a/src/libsodium/include/sodium/utils.h
+++ b/src/libsodium/include/sodium/utils.h
@@ -10,6 +10,12 @@
 extern "C" {
 #endif
 
+#ifndef __cplusplus
+# define _SODIUM_C99(X) (X)
+#else
+# define _SODIUM_C99(X)
+#endif
+
 unsigned char *_sodium_alignedcalloc(unsigned char ** const unaligned_p,
                                      const size_t len);