diff --git a/includes/Hooks.php b/includes/Hooks.php
index 991fd65c..b4b33274 100644
--- a/includes/Hooks.php
+++ b/includes/Hooks.php
@@ -65,6 +65,9 @@ class Hooks implements
 			$updater->addExtensionField( 'linter', 'linter_template',
 				dirname( __DIR__ ) . '/sql/patch-linter-template-tag-fields.sql'
 			);
+			$updater->modifyExtensionField( 'linter', 'linter_params',
+				dirname( __DIR__ ) . '/sql/patch-linter-fix-params-null-definition.sql'
+			);
 		} elseif ( $dbType === 'sqlite' ) {
 			$updater->addExtensionTable( 'linter',
 				dirname( __DIR__ ) . '/sql/sqlite/tables-generated.sql'
@@ -75,6 +78,9 @@ class Hooks implements
 			$updater->addExtensionField( 'linter', 'linter_template',
 				dirname( __DIR__ ) . '/sql/sqlite/patch-linter-template-tag-fields.sql'
 			);
+			$updater->modifyExtensionField( 'linter', 'linter_params',
+				dirname( __DIR__ ) . '/sql/sqlite/patch-linter-fix-params-null-definition.sql'
+			);
 		} elseif ( $dbType === 'postgres' ) {
 			$updater->addExtensionTable( 'linter',
 				dirname( __DIR__ ) . '/sql/postgres/tables-generated.sql'
@@ -85,6 +91,9 @@ class Hooks implements
 			$updater->addExtensionField( 'linter', 'linter_template',
 				dirname( __DIR__ ) . '/sql/postgres/patch-linter-template-tag-fields.sql'
 			);
+			$updater->modifyExtensionField( 'linter', 'linter_params',
+				dirname( __DIR__ ) . '/sql/postgres/patch-linter-fix-params-null-definition.sql'
+			);
 		}
 	}
 
diff --git a/sql/abstractSchemaChanges/patch-linter-fix-params-null-definition.json b/sql/abstractSchemaChanges/patch-linter-fix-params-null-definition.json
new file mode 100644
index 00000000..2ef21346
--- /dev/null
+++ b/sql/abstractSchemaChanges/patch-linter-fix-params-null-definition.json
@@ -0,0 +1,185 @@
+{
+	"comment": "Fix linter table linter_params definition to not be nullable (T327806)",
+	"before": {
+		"name": "linter",
+		"columns": [
+			{
+				"name": "linter_id",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true, "autoincrement": true }
+			},
+			{
+				"name": "linter_page",
+				"comment": "page id",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true }
+			},
+			{
+				"name": "linter_namespace",
+				"comment": "page namespace",
+				"type": "integer",
+				"options": { "notnull": false, "unsigned": false }
+			},
+			{
+				"name": "linter_cat",
+				"comment": "error category (see CategoryManager::$categoryIds)",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true }
+			},
+			{
+				"name": "linter_start",
+				"comment": "end positions of where the error is located",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true }
+			},
+			{
+				"name": "linter_end",
+				"comment": "end positions of where the error is located",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true }
+			},
+			{
+				"name": "linter_params",
+				"comment": "extra parameters about the error, JSON encoded",
+				"type": "blob",
+				"options": { "length": 65530, "notnull": false }
+			},
+			{
+				"name": "linter_template",
+				"comment": "name of a template if used or empty",
+				"type": "binary",
+				"options": { "notnull": true, "length": 255, "default": "" }
+			},
+			{
+				"name": "linter_tag",
+				"comment": "name of tag if used or empty",
+				"type": "binary",
+				"options": { "notnull": true, "length": 32, "default": "" }
+			}
+		],
+		"indexes": [
+			{
+				"name": "linter_page",
+				"comment": "Query by page",
+				"columns": [ "linter_page" ],
+				"unique": false
+			},
+			{
+				"name": "linter_cat_namespace",
+				"comment": "Query by category and namespace",
+				"columns": [ "linter_cat", "linter_namespace" ],
+				"unique": false
+			},
+			{
+				"name": "linter_cat_page_position",
+				"comment": "Unique index for lint errors, also covers linter_cat for query by category",
+				"columns": [ "linter_cat", "linter_page", "linter_start", "linter_end" ],
+				"unique": true
+			},
+			{
+				"name": "linter_cat_template",
+				"comment": "Query by template",
+				"columns": [ "linter_cat", "linter_template" ],
+				"unique": false
+			},
+			{
+				"name": "linter_cat_tag",
+				"comment": "Query by tag",
+				"columns": [ "linter_cat", "linter_tag" ],
+				"unique": false
+			}
+		],
+		"pk": [ "linter_id" ]
+	},
+	"after": {
+		"name": "linter",
+		"columns": [
+			{
+				"name": "linter_id",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true, "autoincrement": true }
+			},
+			{
+				"name": "linter_page",
+				"comment": "page id",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true }
+			},
+			{
+				"name": "linter_namespace",
+				"comment": "page namespace",
+				"type": "integer",
+				"options": { "notnull": false, "unsigned": false }
+			},
+			{
+				"name": "linter_cat",
+				"comment": "error category (see CategoryManager::$categoryIds)",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true }
+			},
+			{
+				"name": "linter_start",
+				"comment": "end positions of where the error is located",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true }
+			},
+			{
+				"name": "linter_end",
+				"comment": "end positions of where the error is located",
+				"type": "integer",
+				"options": { "notnull": true, "unsigned": true }
+			},
+			{
+				"name": "linter_params",
+				"comment": "extra parameters about the error, JSON encoded",
+				"type": "blob",
+				"options": { "length": 65530, "notnull": true }
+			},
+			{
+				"name": "linter_template",
+				"comment": "name of a template if used or empty",
+				"type": "binary",
+				"options": { "notnull": true, "length": 255, "default": "" }
+			},
+			{
+				"name": "linter_tag",
+				"comment": "name of tag if used or empty",
+				"type": "binary",
+				"options": { "notnull": true, "length": 32, "default": "" }
+			}
+		],
+		"indexes": [
+			{
+				"name": "linter_page",
+				"comment": "Query by page",
+				"columns": [ "linter_page" ],
+				"unique": false
+			},
+			{
+				"name": "linter_cat_namespace",
+				"comment": "Query by category and namespace",
+				"columns": [ "linter_cat", "linter_namespace" ],
+				"unique": false
+			},
+			{
+				"name": "linter_cat_page_position",
+				"comment": "Unique index for lint errors, also covers linter_cat for query by category",
+				"columns": [ "linter_cat", "linter_page", "linter_start", "linter_end" ],
+				"unique": true
+			},
+			{
+				"name": "linter_cat_template",
+				"comment": "Query by template",
+				"columns": [ "linter_cat", "linter_template" ],
+				"unique": false
+			},
+			{
+				"name": "linter_cat_tag",
+				"comment": "Query by tag",
+				"columns": [ "linter_cat", "linter_tag" ],
+				"unique": false
+			}
+		],
+		"pk": [ "linter_id" ]
+	}
+}
diff --git a/sql/patch-linter-fix-params-null-definition.sql b/sql/patch-linter-fix-params-null-definition.sql
new file mode 100644
index 00000000..67f5d8ef
--- /dev/null
+++ b/sql/patch-linter-fix-params-null-definition.sql
@@ -0,0 +1,6 @@
+-- This file is automatically generated using maintenance/generateSchemaChangeSql.php.
+-- Source: abstractSchemaChanges/patch-linter-fix-params-null-definition.json
+-- Do not modify this file directly.
+-- See https://www.mediawiki.org/wiki/Manual:Schema_changes
+ALTER TABLE  /*_*/linter
+CHANGE  linter_params linter_params BLOB NOT NULL;
\ No newline at end of file
diff --git a/sql/postgres/patch-linter-fix-params-null-definition.sql b/sql/postgres/patch-linter-fix-params-null-definition.sql
new file mode 100644
index 00000000..147eff25
--- /dev/null
+++ b/sql/postgres/patch-linter-fix-params-null-definition.sql
@@ -0,0 +1,6 @@
+-- This file is automatically generated using maintenance/generateSchemaChangeSql.php.
+-- Source: abstractSchemaChanges/patch-linter-fix-params-null-definition.json
+-- Do not modify this file directly.
+-- See https://www.mediawiki.org/wiki/Manual:Schema_changes
+ALTER TABLE  linter ALTER linter_params
+SET  NOT NULL;
\ No newline at end of file
diff --git a/sql/postgres/tables-generated.sql b/sql/postgres/tables-generated.sql
index 76d6e4ff..bd7b68fc 100644
--- a/sql/postgres/tables-generated.sql
+++ b/sql/postgres/tables-generated.sql
@@ -9,7 +9,7 @@ CREATE TABLE linter (
   linter_cat INT NOT NULL,
   linter_start INT NOT NULL,
   linter_end INT NOT NULL,
-  linter_params TEXT DEFAULT NULL,
+  linter_params TEXT NOT NULL,
   linter_template TEXT DEFAULT '' NOT NULL,
   linter_tag TEXT DEFAULT '' NOT NULL,
   PRIMARY KEY(linter_id)
diff --git a/sql/sqlite/patch-linter-fix-params-null-definition.sql b/sql/sqlite/patch-linter-fix-params-null-definition.sql
new file mode 100644
index 00000000..0766b8f2
--- /dev/null
+++ b/sql/sqlite/patch-linter-fix-params-null-definition.sql
@@ -0,0 +1,18 @@
+-- This file is automatically generated using maintenance/generateSchemaChangeSql.php.
+-- Source: abstractSchemaChanges/patch-linter-fix-params-null-definition.json
+-- Do not modify this file directly.
+-- See https://www.mediawiki.org/wiki/Manual:Schema_changes
+CREATE TEMPORARY TABLE /*_*/__temp__linter AS
+SELECT  linter_id,  linter_page,  linter_namespace,  linter_cat,  linter_start,  linter_end,  linter_params,  linter_template,  linter_tag
+FROM  /*_*/linter;
+DROP  TABLE  /*_*/linter;
+CREATE TABLE  /*_*/linter (    linter_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,    linter_page INTEGER UNSIGNED NOT NULL,    linter_namespace INTEGER DEFAULT NULL,    linter_cat INTEGER UNSIGNED NOT NULL,    linter_start INTEGER UNSIGNED NOT NULL,    linter_end INTEGER UNSIGNED NOT NULL,    linter_params BLOB NOT NULL, linter_template BLOB DEFAULT '' NOT NULL,    linter_tag BLOB DEFAULT '' NOT NULL  );
+INSERT INTO  /*_*/linter (    linter_id, linter_page, linter_namespace,    linter_cat, linter_start, linter_end,    linter_params, linter_template,    linter_tag  )
+SELECT  linter_id,  linter_page,  linter_namespace,  linter_cat,  linter_start,  linter_end,  linter_params,  linter_template,  linter_tag
+FROM  /*_*/__temp__linter;
+DROP  TABLE /*_*/__temp__linter;
+CREATE INDEX linter_page ON  /*_*/linter (linter_page);
+CREATE INDEX linter_cat_namespace ON  /*_*/linter (linter_cat, linter_namespace);
+CREATE UNIQUE INDEX linter_cat_page_position ON  /*_*/linter (    linter_cat, linter_page, linter_start,    linter_end  );
+CREATE INDEX linter_cat_template ON  /*_*/linter (linter_cat, linter_template);
+CREATE INDEX linter_cat_tag ON  /*_*/linter (linter_cat, linter_tag);
\ No newline at end of file
diff --git a/sql/sqlite/tables-generated.sql b/sql/sqlite/tables-generated.sql
index 5dbe9fb9..e07f965e 100644
--- a/sql/sqlite/tables-generated.sql
+++ b/sql/sqlite/tables-generated.sql
@@ -9,7 +9,7 @@ CREATE TABLE /*_*/linter (
   linter_cat INTEGER UNSIGNED NOT NULL,
   linter_start INTEGER UNSIGNED NOT NULL,
   linter_end INTEGER UNSIGNED NOT NULL,
-  linter_params BLOB DEFAULT NULL, linter_template BLOB DEFAULT '' NOT NULL,
+  linter_params BLOB NOT NULL, linter_template BLOB DEFAULT '' NOT NULL,
   linter_tag BLOB DEFAULT '' NOT NULL
 );
 
diff --git a/sql/tables-generated.sql b/sql/tables-generated.sql
index e8631aa3..455fe1e9 100644
--- a/sql/tables-generated.sql
+++ b/sql/tables-generated.sql
@@ -9,7 +9,7 @@ CREATE TABLE /*_*/linter (
   linter_cat INT UNSIGNED NOT NULL,
   linter_start INT UNSIGNED NOT NULL,
   linter_end INT UNSIGNED NOT NULL,
-  linter_params BLOB DEFAULT NULL,
+  linter_params BLOB NOT NULL,
   linter_template VARBINARY(255) DEFAULT '' NOT NULL,
   linter_tag VARBINARY(32) DEFAULT '' NOT NULL,
   INDEX linter_page (linter_page),
diff --git a/sql/tables.json b/sql/tables.json
index feadad65..bc737f7e 100644
--- a/sql/tables.json
+++ b/sql/tables.json
@@ -41,7 +41,7 @@
 				"name": "linter_params",
 				"comment": "extra parameters about the error, JSON encoded",
 				"type": "blob",
-				"options": { "length": 65530, "notnull": false }
+				"options": { "length": 65530, "notnull": true }
 			},
 			{
 				"name": "linter_template",