diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9f3bcccceb9..7795da141d5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2010-09-30  Michael Meissner  <meissner@linux.vnet.ibm.com>
+
+	PR target/45837
+	* config/rs6000/aix.h (TARGET_AIX_OS): Define to be 1.
+	* config/rs6000/rs6000.h (TARGET_AIX_OS): Define to be 0 if not
+	defined.
+	* config/rs6000/option-defaults.h (toplevel): Change #if
+	TARGET_AIX to TARGET_AIX_OS to allow compiler to build after
+	global option changes.
+
 2010-09-30  Jakub Jelinek  <jakub@redhat.com>
 
 	* dwarf2out.c (mem_loc_descriptor): Handle IF_THEN_ELSE.
diff --git a/gcc/config/rs6000/aix.h b/gcc/config/rs6000/aix.h
index f9004b4e6f0..b4134e6214e 100644
--- a/gcc/config/rs6000/aix.h
+++ b/gcc/config/rs6000/aix.h
@@ -24,6 +24,10 @@
 #undef  TARGET_AIX
 #define TARGET_AIX 1
 
+/* Linux64.h wants to redefine TARGET_AIX based on -m64, but it can't be used
+   in the #if conditional in options-default.h, so provide another macro.  */
+#define TARGET_AIX_OS 1
+
 /* AIX always has a TOC.  */
 #define TARGET_NO_TOC 0
 #define TARGET_TOC 1
diff --git a/gcc/config/rs6000/option-defaults.h b/gcc/config/rs6000/option-defaults.h
index 7e117d731da..eb39e0d02d2 100644
--- a/gcc/config/rs6000/option-defaults.h
+++ b/gcc/config/rs6000/option-defaults.h
@@ -27,7 +27,7 @@
 /* This header needs to be included after any other headers affecting
    TARGET_DEFAULT.  */
 
-#if TARGET_AIX
+#if TARGET_AIX_OS
 #define OPT_64 "maix64"
 #define OPT_32 "maix32"
 #else
diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
index a4f9d4b082f..c2f47f2c12c 100644
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -46,6 +46,10 @@
 #define TARGET_AIX 0
 #endif
 
+#ifndef TARGET_AIX_OS
+#define TARGET_AIX_OS 0
+#endif
+
 /* Control whether function entry points use a "dot" symbol when
    ABI_AIX.  */
 #define DOT_SYMBOLS 1