diff --git a/poetry.lock b/poetry.lock
index dcd3514907f2ff1a070f39ebe54cc997cd6160c5..befe9bb6f4818b63bb5ca0d45964a6e4833bb730 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -27,7 +27,7 @@ speedups = ["aiodns", "brotlipy", "cchardet"]
 [[package]]
 category = "dev"
 description = "A small Python module for determining appropriate platform-specific dirs, e.g. a \"user data dir\"."
-marker = "python_version == \"3.6\""
+marker = "python_version >= \"3.6\" and python_version < \"4.0\""
 name = "appdirs"
 optional = false
 python-versions = "*"
@@ -95,7 +95,7 @@ version = "2.0.0"
 [[package]]
 category = "dev"
 description = "The uncompromising code formatter."
-marker = "python_version == \"3.6\""
+marker = "python_version >= \"3.6\" and python_version < \"4.0\""
 name = "black"
 optional = false
 python-versions = ">=3.6"
@@ -342,7 +342,7 @@ six = "*"
 [[package]]
 category = "dev"
 description = "Utility library for gitignore style pattern matching of file paths."
-marker = "python_version == \"3.6\""
+marker = "python_version >= \"3.6\" and python_version < \"4.0\""
 name = "pathspec"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
@@ -551,7 +551,7 @@ version = "5.3"
 [[package]]
 category = "dev"
 description = "Alternative regular expression module, to replace re."
-marker = "python_version == \"3.6\""
+marker = "python_version >= \"3.6\" and python_version < \"4.0\""
 name = "regex"
 optional = false
 python-versions = "*"
@@ -603,7 +603,7 @@ version = "0.10.0"
 [[package]]
 category = "dev"
 description = "a fork of Python 2 and 3 ast modules with type comment support"
-marker = "python_version == \"3.6\""
+marker = "python_version >= \"3.6\" and python_version < \"4.0\""
 name = "typed-ast"
 optional = false
 python-versions = "*"
@@ -667,7 +667,7 @@ docs = ["sphinx", "jaraco.packaging (>=3.2)", "rst.linker (>=1.9)"]
 testing = ["pathlib2", "contextlib2", "unittest2"]
 
 [metadata]
-content-hash = "2e92ad6120327223b363728899edd617103272c023c657b8487f4f6fda938ba8"
+content-hash = "fa67b26290477d18db9a1d00b3e4007168c3a7aaa1491a6e086ed068cfae6d9c"
 python-versions = "^3.5.3"
 
 [metadata.files]
diff --git a/pyproject.toml b/pyproject.toml
index a8af50bfa4c8f8e3041a0937e65fc4eaa91d85a4..29471aaeabb0fa1c063d4b347e81ab6efabc79b4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -21,7 +21,7 @@ texttable = "^1.6"
 PyNaCl = "^1.3"
 
 [tool.poetry.dev-dependencies]
-black = {version = "^19.10b0", allow-prereleases = true, python = "3.6"}
+black = {version = "^19.10b0", python = "^3.6"}
 pre-commit = "^1.18"
 pytest = "^5.1"
 pytest-cov = "^2.7"