diff --git a/spatz/logger.py b/spatz/logger.py
index 5c9de3d..897f2df 100644
--- a/spatz/logger.py
+++ b/spatz/logger.py
@@ -49,12 +49,12 @@ class Logger(Advanceable):
         self.__idx = -1
 
     def _on_step(self, _: float):
-        self.__df = pd.concat([self.__df, pd.Series().copy()], ignore_index=True)
+        self.__df = pd.concat([self.__df, pd.DataFrame()], ignore_index=True)
         self.__idx += 1
         self.__df.loc[self.__idx, 'time'] = self.get_time()
 
     def _on_reset(self):
-        self.__df = pd.DataFrame.from_dict({'time': [self.get_time()]})
+        self.__df = pd.DataFrame.from_dict({'time': [self.get_time()]}).astype(np.float64)
 
     def write(self, attrib: str, value: Any, domain: str = 'all'):
         """Writes a value to the logger.