diff --git a/pySim/ts_51_011.py b/pySim/ts_51_011.py
index cd17ec8b..4d819dd7 100644
--- a/pySim/ts_51_011.py
+++ b/pySim/ts_51_011.py
@@ -435,11 +435,11 @@ class EF_SMSP(LinFixedEF):
             if obj <= 12*60:
                 return obj/5 - 1
             elif obj <= 24*60:
-                return 143 + ((obj - (12 * 60)) / 30)
+                return 143 + ((obj - (12 * 60)) // 30)
             elif obj <= 30 * 24 * 60:
                 return 166 + (obj / (24 * 60))
             elif obj <= 63 * 7 * 24 * 60:
-                return 192 + (obj / (7 * 24 * 60))
+                return 192 + (obj // (7 * 24 * 60))
             else:
                 raise ValueError