diff --git a/pykat/SIfloat.py b/pykat/SIfloat.py
index d6e16ab5a6c0ddbc72ca6a5871571a40d51a5801..91356b583cdb104d2fc3a00764b5bce98754f74e 100644
--- a/pykat/SIfloat.py
+++ b/pykat/SIfloat.py
@@ -31,7 +31,7 @@ def SIfloat(value):
     if value is None: 
         return value
     
-    if value in __exceptions:
+    if str(value) in __exceptions:
         return value
         
     value = np.array(value)