diff --git a/CHANGELOG.md b/CHANGELOG.md
index 748fd9cc..f82d27d7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,8 @@
 
 ### Fixed
 - Standardize germline FORMAT/GQ VCF tag to Integer type (MANTA-1349)
+- Update to pyflow v1.1.20 to close infrequent race condition in task resolution (STREL-853)
+  - Under the race condition error, a non-failing task would be logged as failing with the message "TASKNAME has stopped without a traceable cause"
 
 ## v1.3.1 - 2018-02-19
 
diff --git a/COPYRIGHT.txt b/COPYRIGHT.txt
index 2729aa7f..ed14bec2 100644
--- a/COPYRIGHT.txt
+++ b/COPYRIGHT.txt
@@ -211,7 +211,7 @@ corresponding subdirectories.
 
 ******************************************************************
 
-pyFlow 1.1.19
+pyFlow 1.1.20
 
 pyFlow - a lightweight parallel task engine
 
diff --git a/redist/CMakeLists.txt b/redist/CMakeLists.txt
index 0c77dc69..c11a6bc2 100644
--- a/redist/CMakeLists.txt
+++ b/redist/CMakeLists.txt
@@ -157,7 +157,7 @@ endif ()
 # pyflow
 #
 
-set(PYFLOW_PREFIX "pyflow-1.1.19")
+set(PYFLOW_PREFIX "pyflow-1.1.20")
 set(PYFLOW_DIR "${CMAKE_CURRENT_BINARY_DIR}/${PYFLOW_PREFIX}")
 set(PYFLOW_SCRIPT "${PYFLOW_DIR}/src/pyflow.py")
 
diff --git a/redist/pyflow-1.1.19.tar.bz2 b/redist/pyflow-1.1.19.tar.bz2
deleted file mode 100644
index a0b01153..00000000
Binary files a/redist/pyflow-1.1.19.tar.bz2 and /dev/null differ
diff --git a/redist/pyflow-1.1.20.tar.bz2 b/redist/pyflow-1.1.20.tar.bz2
new file mode 100644
index 00000000..383e21ce
Binary files /dev/null and b/redist/pyflow-1.1.20.tar.bz2 differ