diff --git a/src/iri.c b/src/iri.c
index dc9aa9ad..6c6e8d34 100644
--- a/src/iri.c
+++ b/src/iri.c
@@ -146,7 +146,8 @@ do_conversion (const char *tocode, const char *fromcode, char const *in_org, siz
 
   for (;;)
     {
-      if (iconv (cd, &in, &inlen, out, &outlen) != (size_t)(-1))
+      if (iconv (cd, &in, &inlen, out, &outlen) != (size_t)(-1) &&
+          iconv (cd, NULL, NULL, out, &outlen) != (size_t)(-1))
         {
           *out = s;
           *(s + len - outlen - done) = '\0';