diff --git a/WString.cpp b/WString.cpp
index 2e2a7af..ca06d4e 100755
--- a/WString.cpp
+++ b/WString.cpp
@@ -121,7 +121,8 @@ String::String(double value, unsigned char decimalPlaces)
 
 String::~String()
 {
-  free(buffer);
+  if(buffer)
+    free(buffer);
 }
 
 /*********************************************/