diff --git a/include/polarssl/asn1write.h b/include/polarssl/asn1write.h
index 6116502..1eb7e69 100644
--- a/include/polarssl/asn1write.h
+++ b/include/polarssl/asn1write.h
@@ -29,7 +29,7 @@
 
 #include "asn1.h"
 
-#define ASN1_CHK_ADD(g, f) if( ( ret = f ) < 0 ) return( ret ); else g += ret
+#define ASN1_CHK_ADD(g, f) do { if( ( ret = f ) < 0 ) return( ret ); else g += ret; } while( 0 )
 
 #ifdef __cplusplus
 extern "C" {