diff --git a/hardware/arduino/avr/cores/arduino/WString.cpp b/hardware/arduino/avr/cores/arduino/WString.cpp
index 48c30df77..db79da41f 100644
--- a/hardware/arduino/avr/cores/arduino/WString.cpp
+++ b/hardware/arduino/avr/cores/arduino/WString.cpp
@@ -325,14 +325,14 @@ unsigned char String::concat(unsigned long num)
 unsigned char String::concat(float num)
 {
 	char buf[20];
-	char* string = dtostrf(num, 8, 2, buf);
+	char* string = dtostrf(num, 4, 2, buf);
 	return concat(string, strlen(string));
 }
 
 unsigned char String::concat(double num)
 {
 	char buf[20];
-	char* string = dtostrf(num, 8, 2, buf);
+	char* string = dtostrf(num, 4, 2, buf);
 	return concat(string, strlen(string));
 }
 
diff --git a/hardware/arduino/avr/cores/robot/WString.cpp b/hardware/arduino/avr/cores/robot/WString.cpp
index 48c30df77..db79da41f 100644
--- a/hardware/arduino/avr/cores/robot/WString.cpp
+++ b/hardware/arduino/avr/cores/robot/WString.cpp
@@ -325,14 +325,14 @@ unsigned char String::concat(unsigned long num)
 unsigned char String::concat(float num)
 {
 	char buf[20];
-	char* string = dtostrf(num, 8, 2, buf);
+	char* string = dtostrf(num, 4, 2, buf);
 	return concat(string, strlen(string));
 }
 
 unsigned char String::concat(double num)
 {
 	char buf[20];
-	char* string = dtostrf(num, 8, 2, buf);
+	char* string = dtostrf(num, 4, 2, buf);
 	return concat(string, strlen(string));
 }
 
diff --git a/hardware/arduino/sam/cores/arduino/WString.cpp b/hardware/arduino/sam/cores/arduino/WString.cpp
index d6b344c2a..7b46f05d1 100644
--- a/hardware/arduino/sam/cores/arduino/WString.cpp
+++ b/hardware/arduino/sam/cores/arduino/WString.cpp
@@ -326,14 +326,14 @@ unsigned char String::concat(unsigned long num)
 unsigned char String::concat(float num)
 {
 	char buf[20];
-	char* string = dtostrf(num, 8, 2, buf);
+	char* string = dtostrf(num, 4, 2, buf);
 	return concat(string, strlen(string));
 }
 
 unsigned char String::concat(double num)
 {
 	char buf[20];
-	char* string = dtostrf(num, 8, 2, buf);
+	char* string = dtostrf(num, 4, 2, buf);
 	return concat(string, strlen(string));
 }