diff --git a/tests/platformio.sh b/tests/platformio.sh
index a62fdd798e..21618c79af 100755
--- a/tests/platformio.sh
+++ b/tests/platformio.sh
@@ -12,7 +12,7 @@ function install_platformio()
     ln -s $TRAVIS_BUILD_DIR ~/.platformio/packages/framework-arduinoespressif8266
     # Install dependencies:
     # - esp8266/examples/ConfigFile
-    pio lib install ArduinoJson
+    pio lib install "ArduinoJson@^5.13.4"
 }
 
 function build_sketches_with_platformio()