diff --git a/sonoff/_changelog.ino b/sonoff/_changelog.ino
index 0c13b2ef7..21ceff6b5 100644
--- a/sonoff/_changelog.ino
+++ b/sonoff/_changelog.ino
@@ -1,6 +1,6 @@
 /* 6.2.1.19 20181023
  * Fix header file execution order by renaming user_config.h to my_user_config.h
- * Fix invalid JSON floating point result from nan into null (#4147)
+ * Fix invalid JSON floating point result from nan (Not a Number) and inf (Infinity) into null (#4147)
  *
  * 6.2.1.18 20181019
  * Add more API callbacks and document API.md
diff --git a/sonoff/support.ino b/sonoff/support.ino
index 1e960bb16..83c154834 100644
--- a/sonoff/support.ino
+++ b/sonoff/support.ino
@@ -196,7 +196,7 @@ int TextToInt(char *str)
 
 char* dtostrfd(double number, unsigned char prec, char *s)
 {
-  if (isnan(number)) {
+  if ((isnan(number)) || (isinf(number))) {  // Fix for JSON output (https://stackoverflow.com/questions/1423081/json-left-out-infinity-and-nan-json-status-in-ecmascript)
     strcpy(s, "null");
     return s;
   } else {