diff --git a/nasal_parse.h b/nasal_parse.h
index e2f7636..923b74e 100644
--- a/nasal_parse.h
+++ b/nasal_parse.h
@@ -126,7 +126,7 @@ void nasal_parse::die(uint32_t line,std::string info,bool report_prev=false)
     int col=(int)tokens[ptr].col-(int)tokens[ptr].str.length();
     if(tokens[ptr].type==tok_str)
         col-=2; // tok_str's str has no \"
-    if(report_prev && ptr-1>=0) // used to report lack of ',' ';'
+    if(report_prev && ptr) // used to report lack of ',' ';'
     {
         line=tokens[ptr-1].line;
         col=tokens[ptr-1].col+1;
diff --git a/nasal_vm.h b/nasal_vm.h
index b8dcfc2..9c94968 100644
--- a/nasal_vm.h
+++ b/nasal_vm.h
@@ -122,7 +122,10 @@ protected:
     void opr_mcallh();
     void opr_ret();
 public:
-    nasal_vm():gc(pc,localr,memr,funcr,upvalr,canary,top,stack){}
+    nasal_vm():pc(0),localr(nullptr),memr(nullptr),funcr(nil),
+               upvalr(nil),canary(nullptr),top(stack),
+               num_table(nullptr),str_table(nullptr),
+               gc(pc,localr,memr,funcr,upvalr,canary,top,stack){}
     void run(
         const nasal_codegen&,
         const nasal_import&,