diff --git a/compiler/characterizer/__init__.py b/compiler/characterizer/__init__.py
index 53155e09..4f32beb3 100644
--- a/compiler/characterizer/__init__.py
+++ b/compiler/characterizer/__init__.py
@@ -18,7 +18,7 @@ if not OPTS.analytical_delay:
 
     if OPTS.spice_name != "":
         OPTS.spice_exe=find_exe(OPTS.spice_name)
-        if OPTS.spice_exe=="":
+        if OPTS.spice_exe=="" or OPTS.spice_exe==None:
             debug.error("{0} not found. Unable to perform characterization.".format(OPTS.spice_name),1)
     else:
         (OPTS.spice_name,OPTS.spice_exe) = get_tool("spice",["xa", "hspice", "ngspice", "ngspice.exe"])