diff --git a/src/idna.c b/src/idna.c
index 4638546d..efc5f283 100644
--- a/src/idna.c
+++ b/src/idna.c
@@ -322,6 +322,9 @@ ssize_t uv__idna_toascii(const char* s, const char* se, char* d, char* de) {
   char* ds;
   int rc;
 
+  if (s == se)
+    return UV_EINVAL;
+
   ds = d;
 
   si = s;
diff --git a/test/test-idna.c b/test/test-idna.c
index 5f8d696a..3c4820f7 100644
--- a/test/test-idna.c
+++ b/test/test-idna.c
@@ -115,6 +115,7 @@ TEST_IMPL(utf8_decode1_overrun) {
   ASSERT_PTR_EQ(p, b + 1);
 
   b[0] = 0x7F;
+  ASSERT_EQ(UV_EINVAL, uv__idna_toascii(b, b + 0, c, c + 1));
   ASSERT_EQ(UV_EINVAL, uv__idna_toascii(b, b + 1, c, c + 1));
 
   return 0;