diff --git a/cores/arduino/WString.cpp b/cores/arduino/WString.cpp
index 043fda7c0..9bd9edad6 100644
--- a/cores/arduino/WString.cpp
+++ b/cores/arduino/WString.cpp
@@ -20,6 +20,14 @@
 */
 
 #include "WString.h"
+#include <float.h>
+
+/*********************************************/
+/*  Static Member Initialisation             */
+/*********************************************/
+
+size_t const String::FLT_MAX_DECIMAL_PLACES;
+size_t const String::DBL_MAX_DECIMAL_PLACES;
 
 /*********************************************/
 /*  Constructors                             */
@@ -107,15 +115,19 @@ String::String(unsigned long value, unsigned char base)
 
 String::String(float value, unsigned char decimalPlaces)
 {
+	static size_t const FLOAT_BUF_SIZE = FLT_MAX_10_EXP + FLT_MAX_DECIMAL_PLACES + 1 /* '-' */ + 1 /* '.' */ + 1 /* '\0' */;
 	init();
-	char buf[33];
+	char buf[FLOAT_BUF_SIZE];
+	decimalPlaces = decimalPlaces < FLT_MAX_DECIMAL_PLACES ? decimalPlaces : FLT_MAX_DECIMAL_PLACES;
 	*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
 }
 
 String::String(double value, unsigned char decimalPlaces)
 {
+	static size_t const DOUBLE_BUF_SIZE = DBL_MAX_10_EXP + DBL_MAX_DECIMAL_PLACES + 1 /* '-' */ + 1 /* '.' */ + 1 /* '\0' */;
 	init();
-	char buf[33];
+	char buf[DOUBLE_BUF_SIZE];
+	decimalPlaces = decimalPlaces < DBL_MAX_DECIMAL_PLACES ? decimalPlaces : DBL_MAX_DECIMAL_PLACES;
 	*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
 }
 
diff --git a/cores/arduino/WString.h b/cores/arduino/WString.h
index 2cf4cd747..de2a22977 100644
--- a/cores/arduino/WString.h
+++ b/cores/arduino/WString.h
@@ -50,6 +50,9 @@ class String
 	typedef void (String::*StringIfHelperType)() const;
 	void StringIfHelper() const {}
 
+	static size_t const FLT_MAX_DECIMAL_PLACES = 10;
+	static size_t const DBL_MAX_DECIMAL_PLACES = FLT_MAX_DECIMAL_PLACES;
+
 public:
 	// constructors
 	// creates a copy of the initial value.