Index: head/sys/boot/efi/include/amd64/efibind.h
===================================================================
--- head/sys/boot/efi/include/amd64/efibind.h
+++ head/sys/boot/efi/include/amd64/efibind.h
@@ -85,6 +85,9 @@
 // Basic EFI types of various widths
 //
 
+#ifndef ACPI_THREAD_ID		/* ACPI's definitions are fine */
+#define ACPI_USE_SYSTEM_INTTYPES 1	/* Tell ACPI we've defined types */
+
 typedef uint64_t   UINT64;
 typedef int64_t    INT64;
 
@@ -98,6 +101,7 @@
 typedef uint8_t    UINT8;
 typedef int8_t     INT8;
 
+#endif
 
 #undef VOID
 #define VOID    void
Index: head/sys/boot/efi/include/efidef.h
===================================================================
--- head/sys/boot/efi/include/efidef.h
+++ head/sys/boot/efi/include/efidef.h
@@ -30,7 +30,9 @@
 
 typedef UINT16          CHAR16;
 typedef UINT8           CHAR8;
+#ifndef ACPI_THREAD_ID		/* ACPI's definitions are fine */
 typedef UINT8           BOOLEAN;
+#endif
 
 #ifndef TRUE
     #define TRUE    ((BOOLEAN) 1)
Index: head/sys/boot/efi/include/i386/efibind.h
===================================================================
--- head/sys/boot/efi/include/i386/efibind.h
+++ head/sys/boot/efi/include/i386/efibind.h
@@ -85,6 +85,9 @@
 // Basic EFI types of various widths
 //
 
+#ifndef ACPI_THREAD_ID		/* ACPI's definitions are fine, use those */
+#define ACPI_USE_SYSTEM_INTTYPES 1	/* Tell ACPI we've defined types */
+
 typedef uint64_t   UINT64;
 typedef int64_t    INT64;
 
@@ -98,6 +101,7 @@
 typedef uint8_t    UINT8;
 typedef int8_t     INT8;
 
+#endif
 
 #undef VOID
 #define VOID    void