diff --git a/src/libsodium/crypto_onetimeauth/poly1305/onetimeauth_poly1305.c b/src/libsodium/crypto_onetimeauth/poly1305/onetimeauth_poly1305.c
index e8960dca..28db5663 100644
--- a/src/libsodium/crypto_onetimeauth/poly1305/onetimeauth_poly1305.c
+++ b/src/libsodium/crypto_onetimeauth/poly1305/onetimeauth_poly1305.c
@@ -63,6 +63,12 @@ crypto_onetimeauth_poly1305_keybytes(void)
     return crypto_onetimeauth_poly1305_KEYBYTES;
 }
 
+size_t
+crypto_onetimeauth_poly1305_statebytes(void)
+{
+    return sizeof(crypto_onetimeauth_poly1305_state);
+}
+
 void
 crypto_onetimeauth_poly1305_keygen(
     unsigned char k[crypto_onetimeauth_poly1305_KEYBYTES])
diff --git a/src/libsodium/include/sodium/crypto_onetimeauth_poly1305.h b/src/libsodium/include/sodium/crypto_onetimeauth_poly1305.h
index 325c2d99..479e923d 100644
--- a/src/libsodium/include/sodium/crypto_onetimeauth_poly1305.h
+++ b/src/libsodium/include/sodium/crypto_onetimeauth_poly1305.h
@@ -20,6 +20,9 @@ typedef CRYPTO_ALIGN(16) struct crypto_onetimeauth_poly1305_state {
     unsigned char opaque[256];
 } crypto_onetimeauth_poly1305_state;
 
+SODIUM_EXPORT
+size_t crypto_onetimeauth_poly1305_statebytes(void);
+
 #define crypto_onetimeauth_poly1305_BYTES 16U
 SODIUM_EXPORT
 size_t crypto_onetimeauth_poly1305_bytes(void);