diff -r ef434ea0bcec -r b076f52bd1c8 svghmi/svghmi.py
--- a/svghmi/svghmi.py	Sat Oct 07 17:33:52 2023 +0200
+++ b/svghmi/svghmi.py	Mon Oct 09 16:42:11 2023 +0200
@@ -205,7 +205,7 @@
                 if len(node.path) == 1:
                     extern_variables_declarations += [
                         "extern __IEC_" + node.iectype + "_" +
-                        "t" if node.vartype is "VAR" else "p"
+                        "t" if node.vartype == "VAR" else "p"
                         + node.cpath + ";"]
 
         assert(found_heartbeat)