diff --git a/tf-psa-crypto/drivers/builtin/src/rsa.c b/tf-psa-crypto/drivers/builtin/src/rsa.c
index 8a4c3d048..4f453ef88 100644
--- a/tf-psa-crypto/drivers/builtin/src/rsa.c
+++ b/tf-psa-crypto/drivers/builtin/src/rsa.c
@@ -1257,7 +1257,7 @@ int mbedtls_rsa_public(mbedtls_rsa_context *ctx,
     }
 
     olen = ctx->len;
-    MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&T, &T, &ctx->E, &ctx->N, &ctx->RN));
+    MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod_unsafe(&T, &T, &ctx->E, &ctx->N, &ctx->RN));
     MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&T, output, olen));
 
 cleanup: