diff --git a/teensy/IPAddress.h b/teensy/IPAddress.h
index 3640f5639..4afc62e3f 100644
--- a/teensy/IPAddress.h
+++ b/teensy/IPAddress.h
@@ -63,8 +63,8 @@ class IPAddress : public Printable {
     bool operator==(const uint8_t* addr);
 
     // Overloaded index operator to allow getting and setting individual octets of the address
-    uint8_t operator[](int index) const { return _address.bytes[index]; };
-    uint8_t& operator[](int index) { return _address.bytes[index]; };
+    uint8_t& operator[](const size_t index) { return _address.bytes[index]; }
+    const uint8_t& operator[](const size_t index) const { return _address.bytes[index]; }
 
     // Overloaded copy operators to allow initialisation of IPAddress objects from other types
     IPAddress& operator=(const uint8_t *address);
diff --git a/teensy3/IPAddress.h b/teensy3/IPAddress.h
index c71ea0427..4631593d7 100644
--- a/teensy3/IPAddress.h
+++ b/teensy3/IPAddress.h
@@ -94,12 +94,12 @@ class IPAddress : public Printable {
 	}
 
 	// Overloaded index operator to allow getting and setting individual octets of the address
-	uint8_t operator[](int index) const {
+	uint8_t& operator[](const size_t index) {
 		return _address.bytes[index];
-	};
-	uint8_t& operator[](int index) {
+	}
+	const uint8_t& operator[](const size_t index) const {
 		return _address.bytes[index];
-	};
+	}
 
 	// Overloaded copy operators to allow initialisation of IPAddress objects from other types
 	IPAddress& operator=(const uint8_t *address) {
diff --git a/teensy4/IPAddress.h b/teensy4/IPAddress.h
index c71ea0427..4631593d7 100644
--- a/teensy4/IPAddress.h
+++ b/teensy4/IPAddress.h
@@ -94,12 +94,12 @@ class IPAddress : public Printable {
 	}
 
 	// Overloaded index operator to allow getting and setting individual octets of the address
-	uint8_t operator[](int index) const {
+	uint8_t& operator[](const size_t index) {
 		return _address.bytes[index];
-	};
-	uint8_t& operator[](int index) {
+	}
+	const uint8_t& operator[](const size_t index) const {
 		return _address.bytes[index];
-	};
+	}
 
 	// Overloaded copy operators to allow initialisation of IPAddress objects from other types
 	IPAddress& operator=(const uint8_t *address) {