diff --git a/src/ec/google/chromeec/acpi/battery.asl b/src/ec/google/chromeec/acpi/battery.asl
index d8056b03b2..0a0caec279 100644
--- a/src/ec/google/chromeec/acpi/battery.asl
+++ b/src/ec/google/chromeec/acpi/battery.asl
@@ -17,7 +17,7 @@
 // Scope (EC0)
 
 /* Mutex for EC battery index interface */
-Mutex (BATM, 1)
+Mutex (BATM, 0)
 
 // Wait for desired battery index to be presented in shared memory
 //   Arg0 = battery index