diff --git a/get-certs.sh b/get-certs.sh
index 80dd8f8..25280dd 100755
--- a/get-certs.sh
+++ b/get-certs.sh
@@ -67,7 +67,7 @@ while read -r host; do
   fi
 
   # Hostname to punycode.
-  host=$(echo "$host" | idn)
+  host=$(echo "$host" | idn --allow-unassigned)
 
   # Hostname to lowercase.
   host=$(echo "$host" | tr '[:upper:]' '[:lower:]')
@@ -117,7 +117,7 @@ while read -r host; do
     # If we got a cert back, then the host and port were valid,
     # so they are safe to include in a file name.
     # Convert from punycode to unicode, if needed.
-    host_and_port=$(echo "$host_and_port" | idn --idna-to-unicode)
+    host_and_port=$(echo "$host_and_port" | idn --allow-unassigned --idna-to-unicode)
     echo "$cert" > "certs/${host_and_port}.pem"
     printf ' - OK'
   else