diff --git a/library/x509_csr.c b/library/x509_csr.c
index dbf659b..bdc51a9 100644
--- a/library/x509_csr.c
+++ b/library/x509_csr.c
@@ -115,7 +115,7 @@
     p = mbedtls_calloc( 1, len = buflen );
 
     if( p == NULL )
-        return( MBEDTLS_ERR_X509_ALLOC_FAILED );
+        return( MBEDTLS_ERR_X509_ALLOC_FAILED ); // LCOV_EXCL_LINE
 
     memcpy( p, buf, buflen );