diff --git a/graphql-c_parser/ext/graphql_c_parser_ext/graphql_c_parser_ext.c b/graphql-c_parser/ext/graphql_c_parser_ext/graphql_c_parser_ext.c
index c8a67aede9..e96d772635 100644
--- a/graphql-c_parser/ext/graphql_c_parser_ext/graphql_c_parser_ext.c
+++ b/graphql-c_parser/ext/graphql_c_parser_ext/graphql_c_parser_ext.c
@@ -9,7 +9,7 @@ VALUE GraphQL_CParser_Parser_c_parse(VALUE self) {
   return Qnil;
 }
 
-void Init_graphql_c_parser_ext() {
+void Init_graphql_c_parser_ext(void) {
   VALUE GraphQL = rb_define_module("GraphQL");
   VALUE CParser = rb_define_module_under(GraphQL, "CParser");
   VALUE Lexer = rb_define_module_under(CParser, "Lexer");
diff --git a/graphql-c_parser/ext/graphql_c_parser_ext/graphql_c_parser_ext.h b/graphql-c_parser/ext/graphql_c_parser_ext/graphql_c_parser_ext.h
index 412b395569..0fca80ced2 100644
--- a/graphql-c_parser/ext/graphql_c_parser_ext/graphql_c_parser_ext.h
+++ b/graphql-c_parser/ext/graphql_c_parser_ext/graphql_c_parser_ext.h
@@ -4,5 +4,5 @@
 #include <ruby/encoding.h>
 #include "lexer.h"
 #include "parser.h"
-void Init_graphql_c_parser_ext();
+void Init_graphql_c_parser_ext(void);
 #endif
diff --git a/graphql-c_parser/ext/graphql_c_parser_ext/lexer.c b/graphql-c_parser/ext/graphql_c_parser_ext/lexer.c
index 29246810d0..5b8f80a6c3 100644
--- a/graphql-c_parser/ext/graphql_c_parser_ext/lexer.c
+++ b/graphql-c_parser/ext/graphql_c_parser_ext/lexer.c
@@ -1989,7 +1989,7 @@ var_name = rb_utf8_str_new_cstr(str_content); \
 rb_global_variable(&var_name); \
 rb_str_freeze(var_name); \
 
-void setup_static_token_variables() {
+void setup_static_token_variables(void) {
 	SETUP_STATIC_TOKEN_VARIABLE(ON, "on")
 	SETUP_STATIC_TOKEN_VARIABLE(FRAGMENT, "fragment")
 	SETUP_STATIC_TOKEN_VARIABLE(QUERY, "query")
diff --git a/graphql-c_parser/ext/graphql_c_parser_ext/lexer.h b/graphql-c_parser/ext/graphql_c_parser_ext/lexer.h
index 199628266b..0ff948e0f5 100644
--- a/graphql-c_parser/ext/graphql_c_parser_ext/lexer.h
+++ b/graphql-c_parser/ext/graphql_c_parser_ext/lexer.h
@@ -2,5 +2,5 @@
 #define Graphql_lexer_h
 #include <ruby.h>
 VALUE tokenize(VALUE query_rbstr, int fstring_identifiers, int reject_numbers_followed_by_names, int max_tokens);
-void setup_static_token_variables();
+void setup_static_token_variables(void);
 #endif
diff --git a/graphql-c_parser/ext/graphql_c_parser_ext/lexer.rl b/graphql-c_parser/ext/graphql_c_parser_ext/lexer.rl
index c9d762cca6..5d42aaee80 100644
--- a/graphql-c_parser/ext/graphql_c_parser_ext/lexer.rl
+++ b/graphql-c_parser/ext/graphql_c_parser_ext/lexer.rl
@@ -421,7 +421,7 @@ VALUE tokenize(VALUE query_rbstr, int fstring_identifiers, int reject_numbers_fo
   rb_global_variable(&var_name); \
   rb_str_freeze(var_name); \
 
-void setup_static_token_variables() {
+void setup_static_token_variables(void) {
   SETUP_STATIC_TOKEN_VARIABLE(ON, "on")
   SETUP_STATIC_TOKEN_VARIABLE(FRAGMENT, "fragment")
   SETUP_STATIC_TOKEN_VARIABLE(QUERY, "query")
diff --git a/graphql-c_parser/ext/graphql_c_parser_ext/parser.c b/graphql-c_parser/ext/graphql_c_parser_ext/parser.c
index ac40bb36b3..f7044ffc21 100644
--- a/graphql-c_parser/ext/graphql_c_parser_ext/parser.c
+++ b/graphql-c_parser/ext/graphql_c_parser_ext/parser.c
@@ -75,7 +75,7 @@
 #define YYSTACK_USE_ALLOCA 1
 
 int yylex(YYSTYPE *, VALUE, VALUE);
-void yyerror(VALUE, VALUE, const char*);
+NORETURN(void yyerror(VALUE, VALUE, const char*));
 
 static VALUE GraphQL_Language_Nodes_NONE;
 static VALUE r_string_query;
@@ -3318,7 +3318,7 @@ void yyerror(VALUE parser, VALUE filename, const char *msg) {
     rb_global_variable(&GraphQL_Language_Nodes_##node_class_name); \
     GraphQL_Language_Nodes_##node_class_name = rb_const_get_at(mGraphQLLanguageNodes, rb_intern(#node_class_name));
 
-void initialize_node_class_variables() {
+void initialize_node_class_variables(void) {
   VALUE mGraphQL = rb_const_get_at(rb_cObject, rb_intern("GraphQL"));
   VALUE mGraphQLLanguage = rb_const_get_at(mGraphQL, rb_intern("Language"));
   VALUE mGraphQLLanguageNodes = rb_const_get_at(mGraphQLLanguage, rb_intern("Nodes"));
diff --git a/graphql-c_parser/ext/graphql_c_parser_ext/parser.h b/graphql-c_parser/ext/graphql_c_parser_ext/parser.h
index 1e76a505b9..62cebcad2b 100644
--- a/graphql-c_parser/ext/graphql_c_parser_ext/parser.h
+++ b/graphql-c_parser/ext/graphql_c_parser_ext/parser.h
@@ -1,5 +1,5 @@
 #ifndef Graphql_parser_h
 #define Graphql_parser_h
 int yyparse(VALUE parser, VALUE filename);
-void initialize_node_class_variables();
+void initialize_node_class_variables(void);
 #endif
diff --git a/graphql-c_parser/ext/graphql_c_parser_ext/parser.y b/graphql-c_parser/ext/graphql_c_parser_ext/parser.y
index 83a87685c4..b6b2ef7dff 100644
--- a/graphql-c_parser/ext/graphql_c_parser_ext/parser.y
+++ b/graphql-c_parser/ext/graphql_c_parser_ext/parser.y
@@ -9,7 +9,7 @@
 #define YYSTACK_USE_ALLOCA 1
 
 int yylex(YYSTYPE *, VALUE, VALUE);
-void yyerror(VALUE, VALUE, const char*);
+NORETURN(void yyerror(VALUE, VALUE, const char*));
 
 static VALUE GraphQL_Language_Nodes_NONE;
 static VALUE r_string_query;
@@ -928,7 +928,7 @@ void yyerror(VALUE parser, VALUE filename, const char *msg) {
     rb_global_variable(&GraphQL_Language_Nodes_##node_class_name); \
     GraphQL_Language_Nodes_##node_class_name = rb_const_get_at(mGraphQLLanguageNodes, rb_intern(#node_class_name));
 
-void initialize_node_class_variables() {
+void initialize_node_class_variables(void) {
   VALUE mGraphQL = rb_const_get_at(rb_cObject, rb_intern("GraphQL"));
   VALUE mGraphQLLanguage = rb_const_get_at(mGraphQL, rb_intern("Language"));
   VALUE mGraphQLLanguageNodes = rb_const_get_at(mGraphQLLanguage, rb_intern("Nodes"));