diff --git a/Documentation/firmware-guide/acpi/apei/einj.rst b/Documentation/firmware-guide/acpi/apei/einj.rst
index 55e2331a6438..d6b61d22f525 100644
--- a/Documentation/firmware-guide/acpi/apei/einj.rst
+++ b/Documentation/firmware-guide/acpi/apei/einj.rst
@@ -168,7 +168,7 @@ An error injection example::
   0x00000008	Memory Correctable
   0x00000010	Memory Uncorrectable non-fatal
   # echo 0x12345000 > param1		# Set memory address for injection
-  # echo $((-1 << 12)) > param2		# Mask 0xfffffffffffff000 - anywhere in this page
+  # echo 0xfffffffffffff000 > param2		# Mask - anywhere in this page
   # echo 0x8 > error_type			# Choose correctable memory error
   # echo 1 > error_inject			# Inject now