diff --git a/src/DataIntegrity.php b/src/DataIntegrity.php
index 2031fd6..6ff56e0 100644
--- a/src/DataIntegrity.php
+++ b/src/DataIntegrity.php
@@ -187,10 +187,18 @@ public static function ensureFieldsPresent(dict<string, mixed> $row, table_schem
                     // validate json string
                     $json_obj = \json_decode((string)$row[$field_name]);
                     if ($json_obj is null) {
-                      // invalid json
-                      throw new SQLFakeRuntimeException(
-                        "Invalid value '{$field_value}' for column '{$field_name}' on '{$schema['name']}', expected json",
-                      );
+                      // MySQL will accept the string 'null' in a json column and it converts it to a proper NULL
+                      // the string 'null', however, returns NULL when decoded via \json_decode() which is the same
+                      // as what we get from decoding invalid json
+                      if ((string)$row[$field_name] === 'null') {
+                        $row[$field_name] = null;
+                        $field_value = null;
+                      } else {
+                        // invalid json
+                        throw new SQLFakeRuntimeException(
+                          "Invalid value '{$field_value}' for column '{$field_name}' on '{$schema['name']}', expected json",
+                        );
+                      }
                     }
                   } else {
                     // empty strings are not valid for json columns
diff --git a/tests/InsertQueryTest.php b/tests/InsertQueryTest.php
index 7694486..60880b0 100644
--- a/tests/InsertQueryTest.php
+++ b/tests/InsertQueryTest.php
@@ -260,6 +260,24 @@ final class InsertQueryTest extends HackTest {
       );
   }
 
+  public async function testNullStringCapsInsertIntoJsonColumn(): Awaitable<void> {
+    $conn = static::$conn as nonnull;
+    QueryContext::$strictSQLMode = true;
+    expect(() ==> $conn->query("INSERT INTO table_with_json (id, data) VALUES (1, 'NULL')"))
+      ->toThrow(
+        SQLFakeRuntimeException::class,
+        "Invalid value 'NULL' for column 'data' on 'table_with_json', expected json",
+      );
+  }
+
+  public async function testNullStringLowercaseInsertIntoJsonColumn(): Awaitable<void> {
+    $conn = static::$conn as nonnull;
+    QueryContext::$strictSQLMode = true;
+    await $conn->query("INSERT INTO table_with_json (id, data) VALUES (1, 'null')");
+    $result = await $conn->query('SELECT * FROM table_with_json');
+    expect($result->rows())->toBeSame(vec[dict['id' => 1, 'data' => null]]);
+  }
+
   public async function testNullInsertIntoJsonColumn(): Awaitable<void> {
     $conn = static::$conn as nonnull;
     QueryContext::$strictSQLMode = true;