diff --git a/library/asn1write.c b/library/asn1write.c
index 00ed73c..027c858 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -312,7 +312,9 @@
     {
         // Add new entry if not present yet based on OID
         //
-        if( ( cur = mbedtls_calloc( 1, sizeof(mbedtls_asn1_named_data) ) ) == NULL )
+        cur = (mbedtls_asn1_named_data*)mbedtls_calloc( 1,
+                                            sizeof(mbedtls_asn1_named_data) );
+        if( cur == NULL )
             return( NULL );
 
         cur->oid.len = oid_len;