diff --git a/scripts/retrieve_domains.sh b/scripts/retrieve_domains.sh
index d24731ee3..3ce44cdb8 100644
--- a/scripts/retrieve_domains.sh
+++ b/scripts/retrieve_domains.sh
@@ -62,7 +62,8 @@ main() {
         mkdir -p data/pending
     fi
 
-    # Install idn2 (requires sudo. -qq doesn not work here)
+    # Install idn2 here instead of in $FUNCTION to not bias source processing
+    # time.
     command -v idn2 > /dev/null || sudo apt-get install idn2 > /dev/null
 
     # Download toplist
@@ -223,8 +224,7 @@ process_source_results() {
     sed -i 's/https\?:\/\///; s/\[//; s/\]//' "$source_results"
 
     # Convert Unicode to Punycode
-    idn2 < "$source_results" > temp || exit 1
-    mv temp "$source_results"
+    $FUNCTION --convert-unicode "$source_results"
 
     sort -u "$source_results" -o "$source_results"
 
@@ -441,6 +441,7 @@ ${parked_count},${in_toplist_count},${query_count},${status}" >> "$SOURCE_LOG"
 }
 
 # Call a shell wrapper to to log domain processing events into the domain log.
+# Input:
 #   $1: domains to log either in a file or variable
 #   $2: event type (dead, whitelisted, etc.)
 log_domains() {
@@ -448,6 +449,8 @@ log_domains() {
 }
 
 # Print error message and exit.
+# Input:
+#   $1: error message to print
 error() {
     printf "%s\n" "$1" >&2
     exit 1
diff --git a/scripts/test_functions.sh b/scripts/test_functions.sh
index 987473a14..0b423f890 100644
--- a/scripts/test_functions.sh
+++ b/scripts/test_functions.sh
@@ -294,8 +294,12 @@ test_url_conversion() {
 # Test conversion of Unicode to Punycode
 test_punycode_conversion() {
     input 'ⴰⵣⵓⵍ.bortzmeyer.fr'
+    # Test that entries that may cause idn2 to error are handled properly
+    input 12--5.com
     output xn--4lj0cra7d.bortzmeyer.fr "$RAW"
+    output 12--5.com "$RAW"
     output xn--4lj0cra7d.bortzmeyer.fr "$RAW_LIGHT"
+    output 12--5.com "$RAW_LIGHT"
 }
 
 # Test removal of known dead domains including subdomains
@@ -393,6 +397,7 @@ test_invalid_removal() {
     input invalid-test.100
     input invalid-test.1x
     input invalid-test.com/subfolder
+    input invalid-test-.com
     input i.com
     # Test that invalid subdomains/root domains are not added into the
     # subdomains/root domains files
@@ -410,6 +415,7 @@ test_invalid_removal() {
     output invalid,invalid-test.100 "$DOMAIN_LOG"
     output invalid,invalid-test.1x "$DOMAIN_LOG"
     output invalid,invalid-test.com/subfolder "$DOMAIN_LOG"
+    output invalid,invalid-test-.com "$DOMAIN_LOG"
     output invalid,i.com "$DOMAIN_LOG"
 
     # The validate script does not add invalid entries to the review config
@@ -421,6 +427,7 @@ test_invalid_removal() {
     output invalid-test.100,invalid "$REVIEW_CONFIG"
     output invalid-test.1x,invalid "$REVIEW_CONFIG"
     output invalid-test.com/subfolder,invalid "$REVIEW_CONFIG"
+    output invalid-test-.com,invalid "$REVIEW_CONFIG"
     output i.com,invalid "$REVIEW_CONFIG"
 }
 
@@ -633,6 +640,8 @@ output() {
 }
 
 # Print error message and exit.
+# Input:
+#   $1: error message to print
 error() {
     printf "%s\n" "$1" >&2
     exit 1
diff --git a/scripts/tools.sh b/scripts/tools.sh
index 442938ca4..754f22e28 100644
--- a/scripts/tools.sh
+++ b/scripts/tools.sh
@@ -3,6 +3,7 @@
 # tools.sh is a shell wrapper that stores commonly used functions.
 
 # Function 'format_file' standardizes the format of the given file.
+# Input:
 #   $1: file to be formatted
 format_file() {
     local file="$1"
@@ -46,7 +47,24 @@ format_all() {
     done
 }
 
+# Function 'convert_unicode' converts Unicode to Punycode.
+# Input:
+#   $1: file to process
+convert_unicode() {
+    # Install idn2 (requires sudo. -qq doesn not work here)
+    command -v idn2 > /dev/null || sudo apt-get install idn2 > /dev/null
+
+    # Process the file, handling entries that may cause idn2 to error
+    # https://www.rfc-editor.org/rfc/rfc5891#section-4.2.3.1. If idn2 does
+    # error, exit 1.
+    {
+        grep -vE '\-\.|..--' "$1" | idn2 || exit 1
+        grep -E '\-\.|..--' "$1"
+    } | sort -u -o "$1"
+}
+
 # Function 'log_domains' logs domain processing events into the domain log.
+# Input:
 #   $1: domains to log either in a file or variable
 #   $2: event type (dead, whitelisted, etc.)
 #   $3: source
@@ -73,6 +91,7 @@ log_domains() {
 
 # Function 'prune_lines' prunes lines in the given file to keep its number of
 # lines within the given threshold.
+# Input:
 #   $1: file to be pruned
 #   $2: maximum number of lines to keep
 prune_lines() {
@@ -131,6 +150,7 @@ download_nrd_feed() {
 
 # Function 'send_telegram' sends a Telegram notification with the given
 # message.
+# Input:
 #   $TELEGRAM_CHAT_ID:   Telegram user Chat ID
 #   $TELEGRAM_BOT_TOKEN: Telegram Bot Token
 #   $1: message body
@@ -148,16 +168,19 @@ set -e
 
 case "$1" in
     --format)
-        format_file "$2"
+        format_file "$*"
         ;;
     --format-all)
         format_all
         ;;
+    --convert-unicode)
+        convert_unicode "$*"
+        ;;
     --log-domains)
-        log_domains "$2" "$3" "$4"
+        log_domains "$*"
         ;;
     --prune-lines)
-        prune_lines "$2" "$3"
+        prune_lines "$*"
         ;;
     --download-toplist)
         download_toplist
@@ -166,10 +189,10 @@ case "$1" in
         download_nrd_feed
         ;;
     --send-telegram)
-        send_telegram "$2"
+        send_telegram "$*"
         ;;
     *)
-        printf "\n\e[1;31mInvalid argument: %s\e[0m\n\n" "$1" >&2
+        printf "\n\e[1;31mInvalid argument: %s\e[0m\n\n" "$*" >&2
         exit 1
         ;;
 esac
diff --git a/scripts/update_readme.sh b/scripts/update_readme.sh
index 46de7b152..f252b38c0 100644
--- a/scripts/update_readme.sh
+++ b/scripts/update_readme.sh
@@ -171,6 +171,7 @@ readonly TODAY THIS_MONTH
 
 # Function 'print_stats' is an echo wrapper that returns the formatted
 # statistics for the given source.
+# Input:
 #   $1: source to process (default is all sources)
 print_stats() {
     local this_month total_this_month
@@ -188,6 +189,7 @@ print_stats() {
 
 # Function 'sum' is an echo wrapper that returns the total sum of filtered
 # domains retrieved by the given source for that timeframe.
+# Input:
 #   $1: timeframe to process
 #   $2: source to process (default is all sources)
 sum() {
@@ -201,6 +203,7 @@ sum() {
 
 # Function 'sum_excluded' is an echo wrapper that returns the percentage of
 # excluded domains out of the raw count retrieved by the given source.
+# Input:
 #   $1: source to process (default is all sources)
 sum_excluded() {
     local raw_count white_count dead_count parked_count excluded_count
diff --git a/scripts/validate_domains.sh b/scripts/validate_domains.sh
index df534c285..8390dc209 100644
--- a/scripts/validate_domains.sh
+++ b/scripts/validate_domains.sh
@@ -15,9 +15,6 @@ readonly SUBDOMAINS_TO_REMOVE='config/subdomains.txt'
 readonly DOMAIN_REGEX='[[:alnum:]][[:alnum:].-]*[[:alnum:]]\.[[:alnum:]-]*[a-z]{2,}[[:alnum:]-]*'
 
 main() {
-    # Install idn2 (requires sudo. -qq doesn not work here)
-    command -v idn2 > /dev/null || sudo apt-get install idn2 > /dev/null
-
     # Download toplist
     $FUNCTION --download-toplist
 
@@ -83,9 +80,7 @@ validate() {
     # Convert Unicode to Punycode in raw file and raw light file
     local file
     for file in "$RAW" "$RAW_LIGHT"; do
-        idn2 < "$file" > temp || exit 1
-        mv temp "$file"
-        sort -u "$file" -o "$file"
+        $FUNCTION --convert-unicode "$file"
     done
 
     # Strip away subdomains