diff --git a/README.md b/README.md
index 9d503b14..3aae919c 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,4 @@
-pe-parse
-========
+# pe-parse
 
 [![CI](https://github.com/trailofbits/pe-parse/actions/workflows/ci.yml/badge.svg)](https://github.com/trailofbits/pe-parse/actions/workflows/ci.yml)
 
@@ -30,6 +29,11 @@ the PE file. This should help in constructing a sane parser that allows for dete
 of bogus values in the PE that would result in out of bounds accesses of the input buffer.
 Once data is read from the file it is sanitized and placed in C++ STL containers of internal types.
 
+> [!WARNING]
+> pe-parse's error handling is not thread safe. If you want to perform PE
+> writes/parses in multiple threads, you **must** independently synchronize
+> your operations.
+
 ## Installation
 
 pe-parse can be installed via [vcpkg](https://github.com/microsoft/vcpkg):
diff --git a/pepy/README.md b/pepy/README.md
index 22131199..85495500 100644
--- a/pepy/README.md
+++ b/pepy/README.md
@@ -1,5 +1,5 @@
-pepy
-====
+# pepy
+
 pepy (pronounced p-pie) is a python binding to the pe-parse parser.
 
 pepy supports Python versions 3.6 and above.