diff --git a/internal.h b/internal.h
index bd77ba864c..10775a7e68 100644
--- a/internal.h
+++ b/internal.h
@@ -1109,7 +1109,7 @@ VALUE rb_external_str_with_enc(VALUE str, rb_encoding *eenc);
 #define is_ascii_string(str) (rb_enc_str_coderange(str) == ENC_CODERANGE_7BIT)
 #define is_broken_string(str) (rb_enc_str_coderange(str) == ENC_CODERANGE_BROKEN)
 size_t rb_str_memsize(VALUE);
-VALUE rb_sym_proc_call(VALUE args, VALUE sym, int argc, VALUE *argv, VALUE passed_proc);
+VALUE rb_sym_proc_call(VALUE args, VALUE sym, int argc, const VALUE *argv, VALUE passed_proc);
 
 /* struct.c */
 VALUE rb_struct_init_copy(VALUE copy, VALUE s);
diff --git a/string.c b/string.c
index 5352a6aab1..d80f43d715 100644
--- a/string.c
+++ b/string.c
@@ -8916,7 +8916,7 @@ sym_to_sym(VALUE sym)
 }
 
 VALUE
-rb_sym_proc_call(VALUE args, VALUE sym, int argc, VALUE *argv, VALUE passed_proc)
+rb_sym_proc_call(VALUE args, VALUE sym, int argc, const VALUE *argv, VALUE passed_proc)
 {
     VALUE obj;
 
@@ -8942,7 +8942,8 @@ sym_to_proc(VALUE sym)
     static VALUE sym_proc_cache = Qfalse;
     enum {SYM_PROC_CACHE_SIZE = 67};
     VALUE proc;
-    long id, index;
+    long index;
+    ID id;
     VALUE *aryp;
 
     if (!sym_proc_cache) {