diff --git a/Parser/pegen.c b/Parser/pegen.c
index 82f840c..1941244 100644
--- a/Parser/pegen.c
+++ b/Parser/pegen.c
@@ -7,7 +7,7 @@
 #include "string_parser.h"
 
 PyObject *
-_PyPegen_new_type_comment(Parser *p, char *s)
+_PyPegen_new_type_comment(Parser *p, const char *s)
 {
     PyObject *res = PyUnicode_DecodeUTF8(s, strlen(s), NULL);
     if (res == NULL) {
@@ -26,7 +26,7 @@ _PyPegen_add_type_comment_to_arg(Parser *p, arg_ty a, Token *tc)
     if (tc == NULL) {
         return a;
     }
-    char *bytes = PyBytes_AsString(tc->bytes);
+    const char *bytes = PyBytes_AsString(tc->bytes);
     if (bytes == NULL) {
         return NULL;
     }
@@ -66,7 +66,7 @@ _PyPegen_check_barry_as_flufl(Parser *p, Token* t) {
     assert(t->bytes != NULL);
     assert(t->type == NOTEQUAL);
 
-    char* tok_str = PyBytes_AS_STRING(t->bytes);
+    const char* tok_str = PyBytes_AS_STRING(t->bytes);
     if (p->flags & PyPARSE_BARRY_AS_BDFL && strcmp(tok_str, "<>") != 0) {
         RAISE_SYNTAX_ERROR("with Barry as BDFL, use '<>' instead of '!='");
         return -1;
@@ -78,7 +78,7 @@ _PyPegen_check_barry_as_flufl(Parser *p, Token* t) {
 }
 
 PyObject *
-_PyPegen_new_identifier(Parser *p, char *n)
+_PyPegen_new_identifier(Parser *p, const char *n)
 {
     PyObject *id = PyUnicode_DecodeUTF8(n, strlen(n), NULL);
     if (!id) {
@@ -911,7 +911,7 @@ _PyPegen_expect_soft_keyword(Parser *p, const char *keyword)
     if (t->type != NAME) {
         return NULL;
     }
-    char *s = PyBytes_AsString(t->bytes);
+    const char *s = PyBytes_AsString(t->bytes);
     if (!s) {
         p->error_indicator = 1;
         return NULL;
@@ -942,7 +942,7 @@ _PyPegen_name_from_token(Parser *p, Token* t)
     if (t == NULL) {
         return NULL;
     }
-    char* s = PyBytes_AsString(t->bytes);
+    const char *s = PyBytes_AsString(t->bytes);
     if (!s) {
         p->error_indicator = 1;
         return NULL;
@@ -1068,7 +1068,7 @@ _PyPegen_number_token(Parser *p)
         return NULL;
     }
 
-    char *num_raw = PyBytes_AsString(t->bytes);
+    const char *num_raw = PyBytes_AsString(t->bytes);
     if (num_raw == NULL) {
         p->error_indicator = 1;
         return NULL;
diff --git a/Parser/pegen.h b/Parser/pegen.h
index 1540da0..161a498 100644
--- a/Parser/pegen.h
+++ b/Parser/pegen.h
@@ -202,7 +202,7 @@ CHECK_CALL_NULL_ALLOWED(Parser *p, void *result)
 #define CHECK(type, result) ((type) CHECK_CALL(p, result))
 #define CHECK_NULL_ALLOWED(type, result) ((type) CHECK_CALL_NULL_ALLOWED(p, result))
 
-PyObject *_PyPegen_new_type_comment(Parser *, char *);
+PyObject *_PyPegen_new_type_comment(Parser *, const char *);
 
 Py_LOCAL_INLINE(PyObject *)
 NEW_TYPE_COMMENT(Parser *p, Token *tc)
@@ -210,7 +210,7 @@ NEW_TYPE_COMMENT(Parser *p, Token *tc)
     if (tc == NULL) {
         return NULL;
     }
-    char *bytes = PyBytes_AsString(tc->bytes);
+    const char *bytes = PyBytes_AsString(tc->bytes);
     if (bytes == NULL) {
         goto error;
     }
@@ -242,7 +242,7 @@ INVALID_VERSION_CHECK(Parser *p, int version, char *msg, void *node)
 #define CHECK_VERSION(type, version, msg, node) ((type) INVALID_VERSION_CHECK(p, version, msg, node))
 
 arg_ty _PyPegen_add_type_comment_to_arg(Parser *, arg_ty, Token *);
-PyObject *_PyPegen_new_identifier(Parser *, char *);
+PyObject *_PyPegen_new_identifier(Parser *, const char *);
 Parser *_PyPegen_Parser_New(struct tok_state *, int, int, int, int *, PyArena *);
 void _PyPegen_Parser_Free(Parser *);
 mod_ty _PyPegen_run_parser_from_file_pointer(FILE *, int, PyObject *, const char *,
diff --git a/Parser/string_parser.c b/Parser/string_parser.c
index fa41a36..66405b2 100644
--- a/Parser/string_parser.c
+++ b/Parser/string_parser.c
@@ -87,7 +87,7 @@ decode_unicode_with_escapes(Parser *parser, const char *s, size_t len, Token *t)
         if (*s & 0x80) {
             PyObject *w;
             int kind;
-            void *data;
+            const void *data;
             Py_ssize_t w_len;
             Py_ssize_t i;
             w = decode_utf8(&s, end);
@@ -288,17 +288,17 @@ fstring_find_expr_location(Token *parent, char *expr_str, int *p_lines, int *p_c
     *p_lines = 0;
     *p_cols = 0;
     if (parent && parent->bytes) {
-        char *parent_str = PyBytes_AsString(parent->bytes);
+        const char *parent_str = PyBytes_AsString(parent->bytes);
         if (!parent_str) {
             return false;
         }
-        char *substr = strstr(parent_str, expr_str);
+        const char *substr = strstr(parent_str, expr_str);
         if (substr) {
             // The following is needed, in order to correctly shift the column
             // offset, in the case that (disregarding any whitespace) a newline
             // immediately follows the opening curly brace of the fstring expression.
             bool newline_after_brace = 1;
-            char *start = substr + 1;
+            const char *start = substr + 1;
             while (start && *start != '}' && *start != '\n') {
                 if (*start != ' ' && *start != '\t' && *start != '\f') {
                     newline_after_brace = 0;
@@ -318,7 +318,7 @@ fstring_find_expr_location(Token *parent, char *expr_str, int *p_lines, int *p_c
             }
             /* adjust the start based on the number of newlines encountered
                before the f-string expression */
-            for (char* p = parent_str; p < substr; p++) {
+            for (const char *p = parent_str; p < substr; p++) {
                 if (*p == '\n') {
                     (*p_lines)++;
                 }