diff --git a/composer.json b/composer.json
index 403695e91..599944a49 100644
--- a/composer.json
+++ b/composer.json
@@ -116,7 +116,7 @@
         "test-php7": "tests/test-conversion.sh 70",
         "test-php56": "tests/test-conversion.sh 5",
         "cs-fix": "PHP_CS_FIXER_IGNORE_ENV=1 php -d pcre.jit=0 vendor/bin/php-cs-fixer fix -v",
-        "psalm": "psalm --no-cache --threads=$(nproc)",
+        "psalm": "psalm --no-cache --threads=10",
         "docs": "php tools/build_docs.php",
         "docs-fix": "tools/fix_docs.sh",
         "test": "@php -dzend.assertions=1 -dassert.exception=1 ./vendor/bin/phpunit --coverage-text",