diff --git a/exceptions/MDImporterMissingConcordance.php b/exceptions/MDImporterMissingConcordance.php
index bb9ae96..93252e9 100644
--- a/exceptions/MDImporterMissingConcordance.php
+++ b/exceptions/MDImporterMissingConcordance.php
@@ -11,6 +11,33 @@ final class MDImporterMissingConcordance extends Exception {
 
     /** @var array<string, array<string>> */
     private static array $_missing_concordances = [];
+    public static bool $suppress_shutdown_function = false;
+    private static bool $_shutdown_function_registered = false;
+
+    /**
+     * Gets the text for registering shutdown functions.
+     *
+     * @return string
+     */
+    public static function getCleanMissingConcordanceReport():string {
+
+        if (empty(self::$_missing_concordances)) return '';
+
+
+        $output = PHP_EOL . PHP_EOL . "There are unmapped concordances. Please map them before proceeding." . PHP_EOL . "You may use https://concordance.museum-digital.org/ to do the mapping" . PHP_EOL . PHP_EOL;
+        foreach (self::$_missing_concordances as $key => $values) {
+            sort($values);
+            $output .= PHP_EOL . PHP_EOL . $key . PHP_EOL . PHP_EOL;
+            $output .= implode(PHP_EOL, array_unique($values));
+        }
+        $output .= PHP_EOL;
+
+        // Reset missing concordance report.
+        self::$_missing_concordances = [];
+
+        return $output;
+
+    }
 
     /**
      * Sets up an error.
@@ -24,17 +51,14 @@ final class MDImporterMissingConcordance extends Exception {
 
         if (class_exists("MD_IMPORTER_CONF") && MD_IMPORTER_CONF::$dry_run === true) {
 
-            if (empty(self::$_missing_concordances)) {
+            if (self::$_shutdown_function_registered === false) {
 
                 // Register printing at the end
                 register_shutdown_function(function() {
-                    echo PHP_EOL . PHP_EOL . "There are unmapped concordances. Please map them before proceeding." . PHP_EOL . "You may use https://concordance.museum-digital.org/ to do the mapping" . PHP_EOL . PHP_EOL;
-                    foreach (self::$_missing_concordances as $key => $values) {
-                        sort($values);
-                        echo PHP_EOL . PHP_EOL . $key . PHP_EOL . PHP_EOL;
-                        echo implode(PHP_EOL, array_unique($values));
-                    }
+                    if (self::$suppress_shutdown_function === true) return;
+                    echo self::getCleanMissingConcordanceReport();
                 });
+                self::$_shutdown_function_registered = true;
 
             }