diff --git a/Parser/pegen.c b/Parser/pegen.c
index 24aa3af336..953480df6a 100644
--- a/Parser/pegen.c
+++ b/Parser/pegen.c
@@ -147,7 +147,11 @@ byte_offset_to_character_offset(PyObject *line, Py_ssize_t col_offset)
     if (!str) {
         return 0;
     }
-    assert(col_offset >= 0 && (unsigned long)col_offset <= strlen(str));
+    Py_ssize_t len = strlen(str);
+    if (col_offset > len) {
+        col_offset = len;
+    }
+    assert(col_offset >= 0);
     PyObject *text = PyUnicode_DecodeUTF8(str, col_offset, "replace");
     if (!text) {
         return 0;
@@ -392,10 +396,10 @@ _PyPegen_raise_error(Parser *p, PyObject *errtype, const char *errmsg, ...)
 static PyObject *
 get_error_line(Parser *p, Py_ssize_t lineno)
 {
-    /* If p->tok->fp == NULL, then we're parsing from a string, which means that
-       the whole source is stored in p->tok->str. If not, then we're parsing
-       from the REPL, so the source lines of the current (multi-line) statement
-       are stored in p->tok->stdin_content */
+    /* If the file descriptor is interactive, the source lines of the current
+     * (multi-line) statement are stored in p->tok->interactive_src_start.
+     * If not, we're parsing from a string, which means that the whole source
+     * is stored in p->tok->str. */
     assert(p->tok->fp == NULL || p->tok->fp == stdin);
 
     char *cur_line = p->tok->fp_interactive ? p->tok->interactive_src_start : p->tok->str;