diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index b37da70ea5..b255f90db5 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -7,10 +7,15 @@ in development
 Fixed
 ~~~~~
 
+* Fixed logging middleware to output a ``content_length`` of ``0`` instead of ``Infinity``
+  when the type of data being returned is not supported. Previously, when the value was
+  set to ``Infinity`` this would result in invalid JSON being output into structured
+  logs. (bug fix) #4722
+
+  Contributed by Nick Maludy (@nmaludy Encore Technologies)
 * Fix the workflow execution cancelation to proceed even if the workflow execution is not found or
   completed. (bug fix) #4735
 
-
 3.1.0 - June 27, 2019
 ---------------------
 
diff --git a/st2common/st2common/middleware/logging.py b/st2common/st2common/middleware/logging.py
index 66c32187c7..fa984a60b6 100644
--- a/st2common/st2common/middleware/logging.py
+++ b/st2common/st2common/middleware/logging.py
@@ -99,7 +99,7 @@ def custom_start_response(status, headers, exc_info=None):
         if isinstance(retval, (types.GeneratorType, itertools.chain)):
             # Note: We don't log the result when return value is a generator, because this would
             # result in calling str() on the generator and as such, exhausting it
-            content_length = [float('inf')]
+            content_length = [0]
             log_result = False
 
         # Log the response