diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6aedf8e0..d29f4af6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,10 +7,31 @@ HEAD
 * Fixed `deserializeJson()` silently accepting a `Stream*` (issue #978)
 * Fixed invalid result from `operator|` (issue #981)
 * Made `deserializeJson()` more picky about trailing characters (issue #980)
-* Added `ARDUINOJSON_ENABLE_NAN` to enable NaN in JSON (issue #973)
-* Added `ARDUINOJSON_ENABLE_INFINITY` to enable Infinity in JSON
+* Added `ARDUINOJSON_ENABLE_NAN` (default=0) to enable NaN in JSON (issue #973)
+* Added `ARDUINOJSON_ENABLE_INFINITY` (default=0) to enable Infinity in JSON
 
-> ### BREAKING CHANGE
+> ### BREAKING CHANGES
+> 
+> #### NaN and Infinity
+> 
+> The JSON specification allows neither NaN not Infinity, but previous
+> versions of ArduinoJson supported it. Now, ArduinoJson behaves like most
+> other libraries: a NaN or and Infinity in the `JsonDocument`, becomes
+> a `null` in the output JSON. Also, `deserializeJson()` returns
+> `InvalidInput` if the JSON document contains NaN or Infinity.
+> 
+> This version still supports NaN and Infinity in JSON documents, but
+> it's disabled by default to be compatible with other JSON parsers.
+> If you need the old behavior back, define `ARDUINOJSON_ENABLE_NAN` and
+> `ARDUINOJSON_ENABLE_INFINITY` to `1`;:
+> 
+> ```c++
+> #define ARDUINOJSON_ENABLE_NAN 1
+> #define ARDUINOJSON_ENABLE_INFINITY 1
+> #include <ArduinoJson.h>
+> ```
+> 
+> #### The "or" operator
 > 
 > This version slightly changes the behavior of the | operator when the 
 > variant contains a float and the user requests an integer.
diff --git a/src/ArduinoJson/Configuration.hpp b/src/ArduinoJson/Configuration.hpp
index e98cabc8..588f7f98 100644
--- a/src/ArduinoJson/Configuration.hpp
+++ b/src/ArduinoJson/Configuration.hpp
@@ -137,12 +137,12 @@
 
 // Support NaN in JSON
 #ifndef ARDUINOJSON_ENABLE_NAN
-#define ARDUINOJSON_ENABLE_NAN 1
+#define ARDUINOJSON_ENABLE_NAN 0
 #endif
 
 // Support Infinity in JSON
 #ifndef ARDUINOJSON_ENABLE_INFINITY
-#define ARDUINOJSON_ENABLE_INFINITY 1
+#define ARDUINOJSON_ENABLE_INFINITY 0
 #endif
 
 // Control the exponentiation threshold for big numbers
diff --git a/test/JsonDeserializer/number.cpp b/test/JsonDeserializer/number.cpp
index 1a33074d..45a946cb 100644
--- a/test/JsonDeserializer/number.cpp
+++ b/test/JsonDeserializer/number.cpp
@@ -3,6 +3,8 @@
 // MIT License
 
 #define ARDUINOJSON_USE_LONG_LONG 0
+#define ARDUINOJSON_ENABLE_NAN 1
+#define ARDUINOJSON_ENABLE_INFINITY 1
 
 #include <ArduinoJson.h>
 #include <limits.h>
diff --git a/test/Numbers/parseFloat.cpp b/test/Numbers/parseFloat.cpp
index 4313c0d0..dbdfd454 100644
--- a/test/Numbers/parseFloat.cpp
+++ b/test/Numbers/parseFloat.cpp
@@ -3,6 +3,8 @@
 // MIT License
 
 #define ARDUINOJSON_USE_DOUBLE 0
+#define ARDUINOJSON_ENABLE_NAN 1
+#define ARDUINOJSON_ENABLE_INFINITY 1
 
 #include <ArduinoJson/Numbers/parseFloat.hpp>
 #include <catch.hpp>
diff --git a/test/TextFormatter/writeFloat.cpp b/test/TextFormatter/writeFloat.cpp
index 385051d4..39abe98e 100644
--- a/test/TextFormatter/writeFloat.cpp
+++ b/test/TextFormatter/writeFloat.cpp
@@ -6,6 +6,8 @@
 #include <limits>
 #include <string>
 
+#define ARDUINOJSON_ENABLE_NAN 1
+#define ARDUINOJSON_ENABLE_INFINITY 1
 #include <ArduinoJson/Json/TextFormatter.hpp>
 #include <ArduinoJson/Serialization/DynamicStringWriter.hpp>