diff --git a/composer.json b/composer.json
index 052078efb..a4c741059 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
 		"mediawiki/mediawiki-codesniffer": "28.0.0",
 		"jakub-onderka/php-console-highlighter": "0.3.2",
 		"mediawiki/minus-x": "0.3.2",
-		"mediawiki/mediawiki-phan-config": "0.8.0"
+		"mediawiki/mediawiki-phan-config": "0.9.0"
 	},
 	"scripts": {
 		"test": [
diff --git a/maintenance/MathGenerateTests.php b/maintenance/MathGenerateTests.php
index 0bbf9c79d..74fab331a 100644
--- a/maintenance/MathGenerateTests.php
+++ b/maintenance/MathGenerateTests.php
@@ -77,6 +77,7 @@ class MathGenerateTests extends Maintenance {
 		}
 		$i = 0;
 		foreach ( array_slice( $allEquations, $offset, $length, true ) as $input ) {
+			// @phan-suppress-next-line PhanTypeMismatchArgumentNullable
 			$output = MathRenderer::renderMath( $input[1], $input[2], 'png' );
 			$output = preg_replace( '#src="(.*?)/(([a-f]|\d)*)"#', 'src="\2"', $output );
 			$parserTests[] = [
diff --git a/src/MathInputCheckRestbase.php b/src/MathInputCheckRestbase.php
index 0a0636393..9f510cde9 100644
--- a/src/MathInputCheckRestbase.php
+++ b/src/MathInputCheckRestbase.php
@@ -32,7 +32,7 @@ class MathInputCheckRestbase extends MathInputCheck {
 	 * @see https://phabricator.wikimedia.org/T119300
 	 * @param stdClass $e
 	 * @param MathRenderer|null $errorRenderer
-	 * @return string
+	 * @return string|null
 	 */
 	public function errorObjectToHtml( stdClass $e, $errorRenderer = null ) {
 		if ( $errorRenderer === null ) {
@@ -77,7 +77,7 @@ class MathInputCheckRestbase extends MathInputCheck {
 
 	/**
 	 * Returns the string of the last error.
-	 * @return string
+	 * @return string|null
 	 */
 	public function getError() {
 		$err = $this->restbaseInterface->getError();
diff --git a/src/MathMathML.php b/src/MathMathML.php
index be7ec27b4..70e053052 100644
--- a/src/MathMathML.php
+++ b/src/MathMathML.php
@@ -306,6 +306,7 @@ class MathMathML extends MathRenderer {
 		$this->lastError = '';
 		$requestResult = $this->makeRequest( $host, $post, $res, $this->lastError );
 		if ( $requestResult ) {
+			// @phan-suppress-next-line PhanTypeMismatchArgumentInternal
 			$jsonResult = json_decode( $res );
 			if ( $jsonResult && json_last_error() === JSON_ERROR_NONE ) {
 				if ( $jsonResult->success ) {
diff --git a/src/MathValidator.php b/src/MathValidator.php
index 30ff46df3..0fb0d9bf6 100644
--- a/src/MathValidator.php
+++ b/src/MathValidator.php
@@ -36,7 +36,7 @@ class MathValidator implements ValueValidator {
 		// TeX string is not valid
 		return Result::newError(
 			[
-				Error::newError( null, null, 'malformed-value', [ $checker->getError() ] )
+				Error::newError( '', null, 'malformed-value', [ $checker->getError() ] )
 			]
 		);
 	}
diff --git a/src/MathWikibaseConnector.php b/src/MathWikibaseConnector.php
index 8f7ede00a..13e52eea9 100644
--- a/src/MathWikibaseConnector.php
+++ b/src/MathWikibaseConnector.php
@@ -192,7 +192,7 @@ class MathWikibaseConnector {
 				}
 			}
 
-			if ( $innerInfo ) {
+			if ( $innerInfo && $symbol ) {
 				$innerInfo->setSymbol( $symbol );
 				$output->addHasPartElement( $innerInfo );
 			}