diff --git a/library/pk_wrap.h b/library/pk_wrap.h
index e310005..5dae6b4 100644
--- a/library/pk_wrap.h
+++ b/library/pk_wrap.h
@@ -150,10 +150,12 @@
 int mbedtls_pk_error_from_psa_rsa( psa_status_t status );
 #endif
 
-int mbedtls_pk_psa_sign_ext( psa_algorithm_t psa_alg_md, void *ctx,
-                             const unsigned char *hash, size_t hash_len,
-                             unsigned char *sig, size_t sig_size,
-                             size_t *sig_len );
+#if defined(MBEDTLS_RSA_C)
+int  mbedtls_pk_psa_rsa_sign_ext( psa_algorithm_t psa_alg_md, void *ctx,
+                                  const unsigned char *hash, size_t hash_len,
+                                  unsigned char *sig, size_t sig_size,
+                                  size_t *sig_len );
+#endif /* MBEDTLS_RSA_C */
 
 #endif /* MBEDTLS_PSA_CRYPTO_C */