diff --git a/esphome/core/helpers.cpp b/esphome/core/helpers.cpp
index 2faa6adefb..cbe22dd09a 100644
--- a/esphome/core/helpers.cpp
+++ b/esphome/core/helpers.cpp
@@ -352,8 +352,9 @@ std::string format_mac_address_pretty(const uint8_t *mac) {
 // one is overwritten with '\0', eliminating the per-byte `i < length - 1` check.
 static char *format_hex_internal(char *buffer, size_t buffer_size, const uint8_t *data, size_t length, char separator,
                                  char base) {
-  if (length == 0) {
-    buffer[0] = '\0';
+  if (length == 0 || buffer_size == 0) {
+    if (buffer_size > 0)
+      buffer[0] = '\0';
     return buffer;
   }
   uint8_t stride = separator ? 3 : 2;
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 1185db390e..3c42d7df07 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -1263,15 +1263,13 @@ constexpr uint8_t parse_hex_char(char c) {
 }
 
 /// Convert a nibble (0-15) to hex char with specified base ('a' for lowercase, 'A' for uppercase)
-__attribute__((always_inline)) inline char format_hex_char(uint8_t v, char base) {
-  return v >= 10 ? base + (v - 10) : '0' + v;
-}
+ESPHOME_ALWAYS_INLINE inline char format_hex_char(uint8_t v, char base) { return v >= 10 ? base + (v - 10) : '0' + v; }
 
 /// Convert a nibble (0-15) to lowercase hex char
-__attribute__((always_inline)) inline char format_hex_char(uint8_t v) { return format_hex_char(v, 'a'); }
+ESPHOME_ALWAYS_INLINE inline char format_hex_char(uint8_t v) { return format_hex_char(v, 'a'); }
 
 /// Convert a nibble (0-15) to uppercase hex char (used for pretty printing)
-__attribute__((always_inline)) inline char format_hex_pretty_char(uint8_t v) { return format_hex_char(v, 'A'); }
+ESPHOME_ALWAYS_INLINE inline char format_hex_pretty_char(uint8_t v) { return format_hex_char(v, 'A'); }
 
 /// Write int8 value to buffer without modulo operations.
 /// Buffer must have at least 4 bytes free. Returns pointer past last char written.