diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index f372dc7..a974ca3 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -589,6 +589,7 @@
 		default:
 			printk(TPACPI_ERR "acpi_evalf() called "
 			       "with invalid format character '%c'\n", c);
+			va_end(ap);
 			return 0;
 		}
 	}