diff --git a/uefi-raw/src/table/boot.rs b/uefi-raw/src/table/boot.rs
index 1dc76b67c..c20705b3f 100644
--- a/uefi-raw/src/table/boot.rs
+++ b/uefi-raw/src/table/boot.rs
@@ -439,6 +439,8 @@ impl MemoryType {
 
     /// Construct a custom `MemoryType`. Values in the range `0x8000_0000..=0xffff_ffff` are free for use if you are
     /// an OS loader.
+    ///
+    /// **Warning**: Some EFI firmware versions (e.g., OVMF r11337) may crash or [behave incorrectly](https://wiki.osdev.org/UEFI#My_bootloader_hangs_if_I_use_user_defined_EFI_MEMORY_TYPE_values) when using a custom `MemoryType`.
     #[must_use]
     pub const fn custom(value: u32) -> Self {
         assert!(value >= 0x80000000);