diff --git a/adafruit_datetime.py b/adafruit_datetime.py
index b430f40..cb4fef9 100755
--- a/adafruit_datetime.py
+++ b/adafruit_datetime.py
@@ -1285,15 +1285,15 @@ def _fromtimestamp(cls, t, utc, tz):
         """
         if isinstance(t, float):
             frac, t = _math.modf(t)
+            us = round(frac * 1e6)
+            if us >= 1000000:
+                t += 1
+                us -= 1000000
+            elif us < 0:
+                t -= 1
+                us += 1000000
         else:
-            frac = 0
-        us = round(frac * 1e6)
-        if us >= 1000000:
-            t += 1
-            us -= 1000000
-        elif us < 0:
-            t -= 1
-            us += 1000000
+            us = 0
 
         if utc:
             raise NotImplementedError(