diff --git a/php/libraries/NDB_BVL_Instrument.class.inc b/php/libraries/NDB_BVL_Instrument.class.inc
index 760ef2c6e4b..27942636f5b 100644
--- a/php/libraries/NDB_BVL_Instrument.class.inc
+++ b/php/libraries/NDB_BVL_Instrument.class.inc
@@ -2106,12 +2106,17 @@ abstract class NDB_BVL_Instrument extends NDB_Page
                 ['CID' => $this->getCommentID()]
             );
 
-            $this->instanceData = json_decode($jsondata, true) ?? [];
+            $this->instanceData = json_decode($jsondata ?? '', true) ?? [];
         } else {
             $defaults = $db->pselectRow(
                 "SELECT * FROM $this->table WHERE CommentID=:CID",
                 ['CID' => $this->getCommentID()]
             );
+            // This is only included because it's the primary key. JSON
+            // data does not include it. Unset so that the two types are
+            // consistent. Places that need the commentID should be using
+            // NDB_BVL_Instrument->getCommentID()
+            unset($defaults['CommentID']);
 
             $this->instanceData = $defaults ?? [];
         }
diff --git a/test/unittests/NDB_BVL_Instrument_Test.php b/test/unittests/NDB_BVL_Instrument_Test.php
index a0a7a97b9d0..9027cddeabd 100644
--- a/test/unittests/NDB_BVL_Instrument_Test.php
+++ b/test/unittests/NDB_BVL_Instrument_Test.php
@@ -1141,7 +1141,6 @@ function testGetInstanceData()
                 'ID'                          => '1000',
                 'SessionID'                   => '123',
                 'Test_name'                   => 'Test_name1',
-                'CommentID'                   => 'commentID1',
                 'Data_entry'                  => '',
                 'Required_elements_completed' => 'N',
                 'Administration'              => '',