diff --git a/hardware/arduino/avr/cores/arduino/WString.cpp b/hardware/arduino/avr/cores/arduino/WString.cpp
index 9975303c8e1..f2572d60883 100644
--- a/hardware/arduino/avr/cores/arduino/WString.cpp
+++ b/hardware/arduino/avr/cores/arduino/WString.cpp
@@ -740,6 +740,11 @@ long String::toInt(void) const
 
 float String::toFloat(void) const
 {
-	if (buffer) return float(atof(buffer));
+	return float(toDouble());
+}
+
+double String::toDouble(void) const
+{
+	if (buffer) return atof(buffer);
 	return 0;
 }
diff --git a/hardware/arduino/avr/cores/arduino/WString.h b/hardware/arduino/avr/cores/arduino/WString.h
index de5632c12c1..77709c3ba42 100644
--- a/hardware/arduino/avr/cores/arduino/WString.h
+++ b/hardware/arduino/avr/cores/arduino/WString.h
@@ -190,6 +190,7 @@ class String
 	// parsing/conversion
 	long toInt(void) const;
 	float toFloat(void) const;
+	double toDouble(void) const;
 
 protected:
 	char *buffer;	        // the actual char array
diff --git a/hardware/arduino/sam/cores/arduino/WString.cpp b/hardware/arduino/sam/cores/arduino/WString.cpp
index 533298225e4..71bbc07d13b 100644
--- a/hardware/arduino/sam/cores/arduino/WString.cpp
+++ b/hardware/arduino/sam/cores/arduino/WString.cpp
@@ -742,6 +742,11 @@ long String::toInt(void) const
 
 float String::toFloat(void) const
 {
-	if (buffer) return float(atof(buffer));
+	return float(toDouble());
+}
+
+double String::toDouble(void) const
+{
+	if (buffer) return atof(buffer);
 	return 0;
 }
diff --git a/hardware/arduino/sam/cores/arduino/WString.h b/hardware/arduino/sam/cores/arduino/WString.h
index de5632c12c1..77709c3ba42 100644
--- a/hardware/arduino/sam/cores/arduino/WString.h
+++ b/hardware/arduino/sam/cores/arduino/WString.h
@@ -190,6 +190,7 @@ class String
 	// parsing/conversion
 	long toInt(void) const;
 	float toFloat(void) const;
+	double toDouble(void) const;
 
 protected:
 	char *buffer;	        // the actual char array