diff --git a/.github/scripts/pyspelling.words b/.github/scripts/pyspelling.words
index d71c3c5d8c..dc6e93c8b4 100644
--- a/.github/scripts/pyspelling.words
+++ b/.github/scripts/pyspelling.words
@@ -827,6 +827,7 @@ stateful
 statvfs
 stderr
 stdin
+stdint
 stdout
 Steinar
 Stenberg
@@ -905,6 +906,7 @@ UDP
 UI
 UID
 UIDL
+uint
 Ultrix
 umask
 Unary
diff --git a/docs/INTERNALS.md b/docs/INTERNALS.md
index e1665314c4..41d0387473 100644
--- a/docs/INTERNALS.md
+++ b/docs/INTERNALS.md
@@ -14,7 +14,9 @@ versions of libs and build tools.
 
 We write curl and libcurl to compile with C89 compilers on 32-bit and up
 machines. Most of libcurl assumes more or less POSIX compliance but that is
-not a requirement.
+not a requirement. The compiler must support a 64-bit integer type as well as
+supply a stdint.h header file that defines C99-style fixed-width integer types
+like uint32_t.
 
 We write libcurl to build and work with lots of third party tools, and we
 want it to remain functional and buildable with these and later versions