diff --git a/soc/lowrisc/opentitan/rom_header.S b/soc/lowrisc/opentitan/rom_header.S
index 6bfedafa906..e7b41235dab 100644
--- a/soc/lowrisc/opentitan/rom_header.S
+++ b/soc/lowrisc/opentitan/rom_header.S
@@ -6,16 +6,24 @@
 
 #include <zephyr/toolchain.h>
 
-/* imports */
-GTEXT(__start)
+/* exports */
+GTEXT(__rom_header)
 
-/* OpenTitan manifest consists of 896 bytes (224 words) containing signature,
- * device ID, version info, etc. The test ROM ignores all of these fields
- * except for entry point (final word in manifest).
+/* OpenTitan manifest consists of 1024 bytes (256 words) of manifest
+ * containing signature, device ID, version info, etc. The test ROM
+ * ignores all of these fields except for entry point.
+ *
+ * The layout below conforms to manifest version: 0x71c3 (major),
+ * 0x6c47 (minor).  The manifest format is documented here:
+ * https://github.com/lowRISC/opentitan/blob/689a163294e1791bd30cfe096decf7f9233abad4/sw/host/opentitanlib/src/image/manifest.rs#L205
  */
 SECTION_FUNC(rom_header, __rom_header)
-	.rept(223)
+	.rept(225)
 	.word 0
 	.endr
 	/* Entry point is relative to the beginning of manifest. */
 	.word(__start - __rom_header)
+	/* Extensions entry table goes here. */
+	.rept(30)
+	.word 0
+	.endr