diff --git a/eval.c b/eval.c
index b55a503b..f3b7b5a6 100644
--- a/eval.c
+++ b/eval.c
@@ -1167,6 +1167,14 @@ sexp sexp_close_port_op (sexp ctx, sexp self, sexp_sint_t n, sexp port) {
   return sexp_finalize_port(ctx, self, n, port);
 }
 
+sexp sexp_set_port_line_op (sexp ctx, sexp self, sexp_sint_t n, sexp port, sexp line) {
+  sexp_assert_type(ctx, sexp_iportp, SEXP_IPORT, port);
+  sexp_assert_type(ctx, sexp_fixnump, SEXP_FIXNUM, line);
+  sexp_port_sourcep(port) = 1;
+  sexp_port_line(port) = sexp_unbox_fixnum(line);
+  return SEXP_VOID;
+}
+
 #if SEXP_USE_STATIC_LIBS
 #ifndef PLAN9
 #include "clibs.c"
diff --git a/include/chibi/eval.h b/include/chibi/eval.h
index 063db6db..901d5212 100644
--- a/include/chibi/eval.h
+++ b/include/chibi/eval.h
@@ -115,6 +115,7 @@ SEXP_API sexp sexp_open_output_file_op(sexp ctx, sexp self, sexp_sint_t n, sexp
 SEXP_API sexp sexp_open_binary_input_file(sexp ctx, sexp self, sexp_sint_t n, sexp x);
 SEXP_API sexp sexp_open_binary_output_file(sexp ctx, sexp self, sexp_sint_t n, sexp x);
 SEXP_API sexp sexp_close_port_op(sexp ctx, sexp self, sexp_sint_t n, sexp x);
+SEXP_API sexp sexp_set_port_line_op (sexp ctx, sexp self, sexp_sint_t n, sexp port, sexp line);
 SEXP_API sexp sexp_env_define (sexp ctx, sexp env, sexp sym, sexp val);
 SEXP_API sexp sexp_env_cell (sexp env, sexp sym, int localp);
 SEXP_API sexp sexp_env_ref (sexp env, sexp sym, sexp dflt);
diff --git a/lib/init-7.scm b/lib/init-7.scm
index 95516766..b3b60308 100644
--- a/lib/init-7.scm
+++ b/lib/init-7.scm
@@ -1001,6 +1001,7 @@
      (else
       (call-with-input-file file
         (lambda (in)
+          (set-port-line! in 1)
           (let lp ()
             (let ((x (read in)))
               (cond
diff --git a/opcodes.c b/opcodes.c
index 7af86d4c..97ecbef8 100644
--- a/opcodes.c
+++ b/opcodes.c
@@ -190,6 +190,7 @@ _FN1(_I(SEXP_IPORT), _I(SEXP_STRING), "open-input-string", 0, sexp_make_input_st
 _FN1(_I(SEXP_STRING), _I(SEXP_OPORT), "get-output-string", 0, sexp_get_output_string_op),
 _FN2OPT(_I(SEXP_IPORT), _I(SEXP_FIXNUM), _I(SEXP_BOOLEAN), "open-input-file-descriptor", SEXP_FALSE, sexp_open_input_file_descriptor),
 _FN2OPT(_I(SEXP_OPORT), _I(SEXP_FIXNUM), _I(SEXP_BOOLEAN), "open-output-file-descriptor", SEXP_FALSE, sexp_open_output_file_descriptor),
+_FN2(_I(SEXP_VOID), _I(SEXP_IPORT), _I(SEXP_FIXNUM), "set-port-line!", 0, sexp_set_port_line_op),
 _FN2OPT(_I(SEXP_OBJECT), _I(SEXP_PROCEDURE), _I(SEXP_FIXNUM), "register-optimization!", _I(600), sexp_register_optimization),
 #if SEXP_USE_MATH
 _FN1(_I(SEXP_NUMBER), _I(SEXP_NUMBER), "exp", 0, sexp_exp),