diff --git a/crypto/conf/conf_def.c b/crypto/conf/conf_def.c
index 57d2739ae0c89feae8ea4518d6029a4721a55531..52a87aa76c5f0ad581f3da46a9f42e1109f12c55 100644
--- a/crypto/conf/conf_def.c
+++ b/crypto/conf/conf_def.c
@@ -629,7 +629,7 @@ static int str_copy(CONF *conf, char *section, char **pto, char *from)
 				CONFerr(CONF_F_STR_COPY,CONF_R_VARIABLE_HAS_NO_VALUE);
 				goto err;
 				}
-			BUF_MEM_grow_clean(buf,(strlen(p)+len-(e-from)));
+			BUF_MEM_grow_clean(buf,(strlen(p)+buf->length-(e-from)));
 			while (*p)
 				buf->data[to++]= *(p++);
 			from=e;