diff --git a/src/json/json_parser.cpp b/src/json/json_parser.cpp
index cb30114cb39..cfc636dc4a5 100644
--- a/src/json/json_parser.cpp
+++ b/src/json/json_parser.cpp
@@ -10,7 +10,18 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <fstream>
 
-json_parsert json_parser;
+int yyjsonlex_init_extra(json_parsert *, void **);
+int yyjsonlex_destroy(void *);
+int yyjsonparse(json_parsert &, void *);
+
+bool json_parsert::parse()
+{
+  void *scanner;
+  yyjsonlex_init_extra(this, &scanner);
+  bool parse_fail = yyjsonparse(*this, scanner) != 0;
+  yyjsonlex_destroy(scanner);
+  return parse_fail;
+}
 
 // 'do it all' function
 bool parse_json(
@@ -19,10 +30,10 @@ bool parse_json(
   message_handlert &message_handler,
   jsont &dest)
 {
-  json_parser.clear();
+  json_parsert json_parser{message_handler};
+
   json_parser.set_file(filename);
   json_parser.in=&in;
-  json_parser.log.set_message_handler(message_handler);
 
   bool result=json_parser.parse();
 
diff --git a/src/json/json_parser.h b/src/json/json_parser.h
index 926a30e10bf..132a399a6a5 100644
--- a/src/json/json_parser.h
+++ b/src/json/json_parser.h
@@ -15,21 +15,20 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/parser.h>
 #include <util/json.h>
 
-int yyjsonparse();
-void yyjsonrestart(FILE *input_file);
-
 class json_parsert:public parsert
 {
 public:
+  explicit json_parsert(message_handlert &message_handler)
+    : parsert(message_handler)
+  {
+  }
+
   typedef std::stack<jsont, std::vector<jsont> > stackt;
   stackt stack;
 
   jsont &top() { return stack.top(); }
 
-  virtual bool parse() override
-  {
-    return yyjsonparse()!=0;
-  }
+  bool parse() override;
 
   void push(const jsont &x)
   {
@@ -46,14 +45,9 @@ class json_parsert:public parsert
   virtual void clear() override
   {
     stack=stackt();
-    yyjsonrestart(nullptr);
   }
 };
 
-extern json_parsert json_parser;
-
-int yyjsonerror(const std::string &error);
-
 // 'do it all' functions
 bool parse_json(
   std::istream &in,
diff --git a/src/json/parser.y b/src/json/parser.y
index facaf48638d..fd001f8ab75 100644
--- a/src/json/parser.y
+++ b/src/json/parser.y
@@ -20,11 +20,13 @@
 
 #include <util/unicode.h>
 
-int yyjsonlex();
-extern char *yyjsontext;
-extern int yyjsonleng; // really an int, not a size_t
+int yyjsonlex(void *);
+char *yyjsonget_text(void *);
+#define yyjsontext yyjsonget_text(scanner)
+int yyjsonget_leng(void *); // really an int, not a size_t
+#define yyjsonleng yyjsonget_leng(scanner)
 
-static std::string convert_TOK_STRING()
+static std::string convert_TOK_STRING(void *scanner)
 {
   PRECONDITION(yyjsontext[0]=='"');
   std::size_t len=yyjsonleng;
@@ -70,12 +72,12 @@ static std::string convert_TOK_STRING()
   return result;
 }
 
-static std::string convert_TOK_NUMBER()
+static std::string convert_TOK_NUMBER(void *scanner)
 {
   return yyjsontext;
 }
 
-int yyjsonerror(const std::string &error)
+int yyjsonerror(json_parsert &json_parser, void *scanner, const std::string &error)
 {
   json_parser.parse_error(error, yyjsontext);
   return 0;
@@ -83,6 +85,10 @@ int yyjsonerror(const std::string &error)
 
 %}
 
+%parse-param {json_parsert &json_parser}
+%parse-param {void *scanner}
+%lex-param {void *scanner}
+
 %token TOK_STRING
 %token TOK_NUMBER
 %token TOK_TRUE
@@ -109,7 +115,7 @@ key_value_pair:
           TOK_STRING
         {
           // we abuse the 'value' to temporarily store the key
-          json_parser.top().value=convert_TOK_STRING();
+          json_parser.top().value=convert_TOK_STRING(scanner);
         }
           ':' value
         {
@@ -139,9 +145,9 @@ array_value:
         ;
 
 value   : TOK_STRING
-        { json_parser.push(json_stringt(convert_TOK_STRING())); }
+        { json_parser.push(json_stringt(convert_TOK_STRING(scanner))); }
         | TOK_NUMBER
-        { json_parser.push(json_numbert(convert_TOK_NUMBER())); }
+        { json_parser.push(json_numbert(convert_TOK_NUMBER(scanner))); }
         | object
         | array
         | TOK_TRUE
diff --git a/src/json/scanner.l b/src/json/scanner.l
index c10efc414fb..95e07f8559a 100755
--- a/src/json/scanner.l
+++ b/src/json/scanner.l
@@ -11,8 +11,9 @@
 %option noinput
 %option nounistd
 %option never-interactive
-
 %option noyywrap
+%option reentrant
+%option extra-type="json_parsert *"
 
 %{
 
@@ -24,7 +25,7 @@
 #pragma warning(disable:4005)
 #endif
 
-#define PARSER json_parser
+#define PARSER (*yyextra)
 
 #include "json_parser.h"
 #include "json_y.tab.h"