diff --git a/freqtrade/optimize/hyperopt_interface.py b/freqtrade/optimize/hyperopt_interface.py
index 622de3015..08823ece0 100644
--- a/freqtrade/optimize/hyperopt_interface.py
+++ b/freqtrade/optimize/hyperopt_interface.py
@@ -20,6 +20,7 @@ class IHyperOpt(ABC):
         stoploss -> float: optimal stoploss designed for the strategy
         ticker_interval -> int: value of the ticker interval to use for the strategy
     """
+    ticker_interval: str
 
     @staticmethod
     @abstractmethod
diff --git a/freqtrade/resolvers/hyperopt_resolver.py b/freqtrade/resolvers/hyperopt_resolver.py
index 638148ee2..9333bb09a 100644
--- a/freqtrade/resolvers/hyperopt_resolver.py
+++ b/freqtrade/resolvers/hyperopt_resolver.py
@@ -33,7 +33,7 @@ class HyperOptResolver(IResolver):
         self.hyperopt = self._load_hyperopt(hyperopt_name, extra_dir=config.get('hyperopt_path'))
 
         # Assign ticker_interval to be used in hyperopt
-        self.hyperopt.__class__.ticker_interval = config.get('ticker_interval')
+        self.hyperopt.__class__.ticker_interval = str(config['ticker_interval'])
 
         if not hasattr(self.hyperopt, 'populate_buy_trend'):
             logger.warning("Custom Hyperopt does not provide populate_buy_trend. "