diff --git a/README.md b/README.md
index 83a524bbd..8361157b4 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,10 @@ and run it with:
 java -jar /path/to/google-java-format-${GJF_VERSION?}-all-deps.jar <options> [files...]
 ```
 
+Note that it uses the `jdk.compiler` module to parse the Java source code. The `java` binary
+version used must therefore be from a JDK (not JRE) that's at least as big as the files being formatted.
+An alternative is to use the available GraalVM based native binaries instead.
+
 The formatter can act on whole files, on limited lines (`--lines`), on specific
 offsets (`--offset`), passing through to standard-out (default) or altered
 in-place (`--replace`).