diff --git a/src/lexer.cpp b/src/lexer.cpp
index 33a25fe0..60807907 100644
--- a/src/lexer.cpp
+++ b/src/lexer.cpp
@@ -292,12 +292,12 @@ static bool is_unicode_Lo_char(uint32_t c) {
         char* p_end;
 
         try{
-            float_out = std::strtod(text.begin(), &p_end);
+            float_out = std::strtod(text.data(), &p_end);
         }catch(...){
             SyntaxError("invalid number literal");
         }
         
-        if(p_end == text.end()){
+        if(p_end == text.data() + text.size()){
             add_token(TK("@num"), (f64)float_out);
             return;
         }
diff --git a/src/pocketpy.cpp b/src/pocketpy.cpp
index 10ac5e43..fac6064e 100644
--- a/src/pocketpy.cpp
+++ b/src/pocketpy.cpp
@@ -502,7 +502,7 @@ void init_builtins(VM* _vm) {
             double float_out;
             char* p_end;
             try{
-                float_out = std::strtod(s.begin(), &p_end);
+                float_out = std::strtod(s.data, &p_end);
                 PK_ASSERT(p_end == s.end());
             }catch(...){
                 vm->ValueError("invalid literal for float(): " + s.escape());