diff --git a/src/frontend/parse-bison-y.h b/src/frontend/parse-bison-y.h
index 7ed0f93e1..aa1c32cc4 100644
--- a/src/frontend/parse-bison-y.h
+++ b/src/frontend/parse-bison-y.h
@@ -3,7 +3,6 @@ struct PPltype {
 };
 
 extern int PPlex(YYSTYPE *lvalp, struct PPltype *llocp, char **line);
-extern int PPdebug;
 
 extern struct pnode *PP_mkunode(int op, struct pnode *arg);
 extern struct pnode *PP_mkfnode(const char *func, struct pnode *arg);
diff --git a/src/frontend/parse-bison.y b/src/frontend/parse-bison.y
index c99466761..f064386dc 100644
--- a/src/frontend/parse-bison.y
+++ b/src/frontend/parse-bison.y
@@ -29,6 +29,7 @@
   static void PPerror (YYLTYPE *locp, char **line, struct pnode **retval, char const *);
 %}
 
+%require "2.7"
 %name-prefix "PP"
 
 %defines
diff --git a/src/frontend/parse.c b/src/frontend/parse.c
index d27b0103e..9369a3cf6 100644
--- a/src/frontend/parse.c
+++ b/src/frontend/parse.c
@@ -22,8 +22,6 @@ Author: 1985 Wayne A. Christopher, U. C. Berkeley CAD Group
 
 static bool checkvalid(struct pnode *pn);
 
-extern int PPparse(char **, struct pnode **);
-
 void db_print_pnode_tree(struct pnode *p, char *print);
 
 
diff --git a/src/spicelib/parser/inpptree-parser-y.h b/src/spicelib/parser/inpptree-parser-y.h
index 60b86ec33..e72b39442 100644
--- a/src/spicelib/parser/inpptree-parser-y.h
+++ b/src/spicelib/parser/inpptree-parser-y.h
@@ -3,7 +3,6 @@ struct PTltype {
 };
 
 extern int PTlex(YYSTYPE *lvalp, struct PTltype *llocp, char **line);
-extern int PTdebug;
 
 extern INPparseNode *PT_mkbnode(const char *opstr, INPparseNode *arg1, INPparseNode *arg2);
 extern INPparseNode *PT_mkfnode(const char *fname, INPparseNode *arg);
diff --git a/src/spicelib/parser/inpptree-parser.y b/src/spicelib/parser/inpptree-parser.y
index c1abe7c1d..c12f0963d 100644
--- a/src/spicelib/parser/inpptree-parser.y
+++ b/src/spicelib/parser/inpptree-parser.y
@@ -28,6 +28,7 @@
   static void PTerror (YYLTYPE *locp, char **line, struct INPparseNode **retval, void *ckt, char const *);
 %}
 
+%require "2.7"
 %name-prefix "PT"
 
 %defines
diff --git a/src/spicelib/parser/inpptree.c b/src/spicelib/parser/inpptree.c
index 705e2f09e..041a641ee 100644
--- a/src/spicelib/parser/inpptree.c
+++ b/src/spicelib/parser/inpptree.c
@@ -14,8 +14,6 @@ Author: 1987 Wayne A. Christopher, U. C. Berkeley CAD Group
 #include "inpptree-parser.h"
 #include "inpptree-parser-y.h"
 
-int PTparse(char **line, INPparseNode **p, CKTcircuit *ckt);
-
 static INPparseNode *mkcon(double value);
 static INPparseNode *mkb(int type, INPparseNode * left,
                          INPparseNode * right);