diff --git a/CHANGELOG.md b/CHANGELOG.md
index 37d0ebc38..e57cc61d8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,9 +4,12 @@ Changelog
 NOTE: isort follows the [semver](https://semver.org/) versioning standard.
 Find out more about isort's release policy [here](https://pycqa.github.io/isort/docs/major_releases/release_policy/).
 
-### 5.6.3 October TBD, 2020
+### 5.6.4 October TBD, 2020
   - Fixed #1556: Empty line added between imports that should be skipped.
 
+### 5.6.3 October 11, 2020
+  - Improved packaging of test files alongside source distribution (see: https://github.com/PyCQA/isort/pull/1555).
+
 ### 5.6.2 October 10, 2020
   - Fixed #1548: On rare occasions an unecessary empty line can be added when an import is marked as skipped.
   - Fixed #1542: Bug in VERTICAL_PREFIX_FROM_MODULE_IMPORT wrap mode.
diff --git a/docs/contributing/4.-acknowledgements.md b/docs/contributing/4.-acknowledgements.md
index 9f0ccae89..73f2b3f76 100644
--- a/docs/contributing/4.-acknowledgements.md
+++ b/docs/contributing/4.-acknowledgements.md
@@ -200,6 +200,7 @@ Code Contributors
 - Andrew Howe (@howeaj)
 - Sang-Heon Jeon (@lntuition)
 - Denis Veselov (@saippuakauppias)
+- James Curtin (@jamescurtin)
 
 Documenters
 ===================
diff --git a/isort/_version.py b/isort/_version.py
index 8d9ad75cd..06497b9f5 100644
--- a/isort/_version.py
+++ b/isort/_version.py
@@ -1 +1 @@
-__version__ = "5.6.2"
+__version__ = "5.6.3"
diff --git a/pyproject.toml b/pyproject.toml
index a5ffa0381..a91cea2ab 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,7 +3,7 @@ line-length = 100
 
 [tool.poetry]
 name = "isort"
-version = "5.6.2"
+version = "5.6.3"
 description = "A Python utility / library to sort Python imports."
 authors = ["Timothy Crosley <timothy.crosley@gmail.com>"]
 license = "MIT"
@@ -33,7 +33,9 @@ classifiers = [
 urls = { Changelog = "https://github.com/pycqa/isort/blob/master/CHANGELOG.md" }
 packages = [
     { include = "isort" },
-    { include = "tests", format = "sdist" },
+]
+include = [
+    { path = "tests", format = "sdist" },
 ]
 
 [tool.poetry.dependencies]
@@ -99,5 +101,5 @@ logo = "art/logo.png"
 palette = {scheme = "isort"}
 
 [build-system]
-requires = ["poetry>=0.12"]
-build-backend = "poetry.masonry.api"
+requires = ["poetry-core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"