diff --git a/saqc/core/translation/basescheme.py b/saqc/core/translation/basescheme.py
index b5ce8f2aff3e54954843b7559ec9477e26559d54..cf3f0ab78846e210f634c5d0717b06a72b2112ad 100644
--- a/saqc/core/translation/basescheme.py
+++ b/saqc/core/translation/basescheme.py
@@ -148,7 +148,7 @@ class MappingScheme(TranslationScheme):
             if flag not in self._backward:
                 raise ValueError(f"invalid flag: {flag}")
             return float(flag)
-        return self._forward[flag]
+        return float(self._forward[flag])
 
     def forward(self, flags: pd.DataFrame | DictOfSeries | pd.Series) -> Flags:
         """