diff --git a/src/cs_gen.cc b/src/cs_gen.cc
index f18ab368..de9d8b90 100644
--- a/src/cs_gen.cc
+++ b/src/cs_gen.cc
@@ -1066,8 +1066,8 @@ static void compile_cmd(
             case '3':
             case '4':
                 if (more && (numargs < MaxArguments)) {
-                    int numrep = *fmt - '0' + 1;
-                    fmt -= numrep;
+                    int numrep = -int(*fmt) + '0' - 1;
+                    fmt = ostd::string_range{&fmt[numrep], &fmt[fmt.size()]};
                     rep = true;
                 } else {
                     while (numargs > MaxArguments) {
diff --git a/src/cs_util.cc b/src/cs_util.cc
index 46d960b8..6500aa95 100644
--- a/src/cs_util.cc
+++ b/src/cs_util.cc
@@ -75,7 +75,7 @@ cs_int cs_parse_int(ostd::string_range input, ostd::string_range *end) {
         ++past;
     }
 done:
-    if (past.equals_front(input)) {
+    if (&past[0] == &input[0]) {
         p_set_end(orig, end);
     } else {
         p_set_end(past, end);
diff --git a/src/cs_vm.cc b/src/cs_vm.cc
index 49029103..b323e571 100644
--- a/src/cs_vm.cc
+++ b/src/cs_vm.cc
@@ -451,7 +451,9 @@ static inline void callcommand(
             case '3':
             case '4':
                 if (i + 1 < numargs) {
-                    fmt -= *fmt - '0' + 1;
+                    fmt = ostd::string_range{
+                        &fmt[-int(*fmt) + '0' - 1], &fmt[fmt.size()]
+                    };
                     rep = true;
                 }
                 break;