diff --git a/libcst/codemod/_cli.py b/libcst/codemod/_cli.py
index d4ced900..cb9c8529 100644
--- a/libcst/codemod/_cli.py
+++ b/libcst/codemod/_cli.py
@@ -590,7 +590,7 @@ def parallel_exec_transform_with_prettyprint(  # noqa: C901
     progress = Progress(enabled=not hide_progress, total=total)
 
     # Grab number of cores if we need to
-    jobs: int = jobs or cpu_count()
+    jobs: int = jobs if jobs is not None else cpu_count()
 
     if jobs < 1:
         raise Exception("Must have at least one job to process!")
@@ -598,7 +598,7 @@ def parallel_exec_transform_with_prettyprint(  # noqa: C901
     if total == 0:
         return ParallelTransformResult(successes=0, failures=0, skips=0, warnings=0)
 
-    if repo_root:
+    if repo_root is not None:
         # Make sure if there is a root that we have the absolute path to it.
         repo_root = os.path.abspath(repo_root)
         # Spin up a full repo metadata manager so that we can provide metadata
diff --git a/libcst/codemod/commands/convert_format_to_fstring.py b/libcst/codemod/commands/convert_format_to_fstring.py
index 39b2f96c..29e81246 100644
--- a/libcst/codemod/commands/convert_format_to_fstring.py
+++ b/libcst/codemod/commands/convert_format_to_fstring.py
@@ -295,7 +295,7 @@ class ConvertFormatStringCommand(VisitorBasedCodemodCommand):
                         spec_format_spec,
                         spec_conversion,
                     ) in format_spec_tokens:
-                        if spec_format_spec:
+                        if spec_format_spec is not None:
                             # This shouldn't be possible, we don't allow it in the spec!
                             raise Exception("Logic error!")
                         if spec_literal_text:
diff --git a/libcst/codemod/visitors/_apply_type_annotations.py b/libcst/codemod/visitors/_apply_type_annotations.py
index 77beac8b..2090c151 100644
--- a/libcst/codemod/visitors/_apply_type_annotations.py
+++ b/libcst/codemod/visitors/_apply_type_annotations.py
@@ -20,7 +20,7 @@ def _get_import_alias_names(import_aliases: Sequence[cst.ImportAlias]) -> Set[st
     import_names = set()
     for imported_name in import_aliases:
         asname = imported_name.asname
-        if asname:
+        if asname is not None:
             import_names.add(get_full_name_for_node(asname.name))
         else:
             import_names.add(get_full_name_for_node(imported_name.name))
@@ -242,7 +242,9 @@ class ApplyTypeAnnotationsVisitor(ContextAwareTransformer):
         super().__init__(context)
         # Qualifier for storing the canonical name of the current function.
         self.qualifier: List[str] = []
-        self.annotations: Annotations = annotations or Annotations()
+        self.annotations: Annotations = (
+            Annotations() if annotations is None else annotations
+        )
         self.toplevel_annotations: Dict[str, cst.Annotation] = {}
         self.visited_classes: Set[str] = set()
         self.overwrite_existing_annotations = overwrite_existing_annotations
@@ -297,7 +299,7 @@ class ApplyTypeAnnotationsVisitor(ContextAwareTransformer):
         context_contents = self.context.scratch.get(
             ApplyTypeAnnotationsVisitor.CONTEXT_KEY
         )
-        if context_contents:
+        if context_contents is not None:
             stub, overwrite_existing_annotations = context_contents
             self.overwrite_existing_annotations = (
                 self.overwrite_existing_annotations or overwrite_existing_annotations
diff --git a/libcst/helpers/_statement.py b/libcst/helpers/_statement.py
index 4a3825f2..a9431b44 100644
--- a/libcst/helpers/_statement.py
+++ b/libcst/helpers/_statement.py
@@ -31,7 +31,7 @@ def get_absolute_module_for_import(
         return None
     base_module = ".".join(modules[:-num_dots])
     # Finally, if the module name was supplied, append it to the end.
-    if module_name:
+    if module_name is not None:
         # If we went all the way to the top, the base module should be empty, so we
         # should return the relative bit as absolute. Otherwise, combine the base
         # module and module name using a dot separator.
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 84fd1d13..2f86e9b3 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,12 +1,12 @@
-black>=19.10b0
+black==20.8b1
 codecov>=2.1.4
 coverage>=4.5.4
-fixit>=0.1.0
+fixit==0.1.1
 flake8>=3.7.8
 hypothesis>=4.36.0
 hypothesmith>=0.0.4
 git+https://github.com/jimmylai/sphinx.git@slots_type_annotation
-isort>=4.3.20
+isort==5.5.3
 jupyter>=1.0.0
 nbsphinx>=0.4.2
 pyre-check==0.0.41