diff --git a/SConstruct b/SConstruct
index e0026125..4fdad144 100644
--- a/SConstruct
+++ b/SConstruct
@@ -213,7 +213,7 @@ if 'NSIS_CONFIG_CONST_DATA_PATH' in defenv['NSIS_CPPDEFINES']:
 	defenv.Append(NSIS_CPPDEFINES = [('PREFIX_DATA', '"%s"' % defenv.subst('$PREFIX_DATA'))])
 	defenv.Append(NSIS_CPPDEFINES = [('PREFIX_DOC', '"%s"' % defenv.subst('$PREFIX_DOC'))])
 
-if defenv.get('SOURCE_DATE_EPOCH','') is not '':
+if defenv.get('SOURCE_DATE_EPOCH','') != '':
 	defenv['ENV']['SOURCE_DATE_EPOCH'] = defenv['SOURCE_DATE_EPOCH'] = int(defenv['SOURCE_DATE_EPOCH'], 0) # Normalize and apply to ENV for child processes
 	defenv.Append(NSIS_CPPDEFINES = [('NSIS_SOURCE_DATE_EPOCH', '%s' % defenv['SOURCE_DATE_EPOCH'])]) # Display in /HDRINFO