diff --git a/composed_configuration/_sentry.py b/composed_configuration/_sentry.py
index 13402be..58b687e 100644
--- a/composed_configuration/_sentry.py
+++ b/composed_configuration/_sentry.py
@@ -29,4 +29,6 @@ def mutate_configuration(configuration: Type[ComposedConfiguration]) -> None:
 
     SENTRY_RELEASE = values.Value(None)
 
-    SENTRY_TRACES_SAMPLE_RATE = values.Value(None)
+    # None is a valid default value, but if this is set via environment variable,
+    # the value must be interpretable as a float
+    SENTRY_TRACES_SAMPLE_RATE = values.FloatValue(None)