diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index 85d634a..1a027d6 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -5216,7 +5216,7 @@
     mbedtls_mpi_uint carry = 0;
 
     if (X_limbs != 2 * P521_WIDTH || X[2 * P521_WIDTH - 1] != 0) {
-       return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
+        return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
     }
 
     /* Step 1: Reduction to P521_WIDTH limbs */