diff --git a/php/libraries/CSVParser.class.inc b/php/libraries/CSVParser.class.inc
index 3ff04c382c7..53b97144886 100644
--- a/php/libraries/CSVParser.class.inc
+++ b/php/libraries/CSVParser.class.inc
@@ -37,17 +37,18 @@ class CSVParser
     /**
      * Check that headers match (equivalent arrays)
      *
-     * @param array $headers         Headers parsed from csv file
-     * @param array $expectedHeaders Expected headers (ex: from instrument)
-     * @param bool  $strict          If true, $headers cannot be a superset
-     *                               of $expectedHeaders
+     * @param array|false $headers         Headers parsed from csv file
+     * @param array       $expectedHeaders Expected headers (ex: from instrument)
+     * @param bool        $strict          If true, $headers cannot be a superset
+     *                                     of $expectedHeaders
      *
-     * @return bool                  Returns true if headers are valid
+     * @return bool                        Returns true if headers are valid
      */
     private function _validateHeaders(
-        array $headers, array $expectedHeaders, bool $strict = false
+        array|false $headers, array $expectedHeaders, bool $strict = false
     ): bool {
-        if ($strict && count($headers) !== count($expectedHeaders)) {
+        if (!$headers || ($strict && count($headers) !== count($expectedHeaders))
+        ) {
             return false;
         }
 
diff --git a/php/libraries/InstrumentDataParser.class.inc b/php/libraries/InstrumentDataParser.class.inc
index 13c4f37768a..a36a261e607 100644
--- a/php/libraries/InstrumentDataParser.class.inc
+++ b/php/libraries/InstrumentDataParser.class.inc
@@ -75,10 +75,7 @@ class InstrumentDataParser extends CSVParser
     ): array {
         return array_merge(
             ['PSCID', 'Visit_label'],   // SessionID
-            // Convert to static list of flag fields
-            // List: Data_entry, Required_elements_completed, Administration,
-            //       Validity, Exclusion, Testdate
-            self::getFlagHeaders(   // Whitelist would prevent invalid columns
+            self::getFlagHeaders(
                 [
                     'ID', 'SessionID', 'Test_name', 'TestID',
                     'CommentID', 'UserID', 'Data', 'DataID',