diff --git a/c/src/lib/libcpu/powerpc/ChangeLog b/c/src/lib/libcpu/powerpc/ChangeLog
index 5edcf197f9..9f70d9edfd 100644
--- a/c/src/lib/libcpu/powerpc/ChangeLog
+++ b/c/src/lib/libcpu/powerpc/ChangeLog
@@ -1,3 +1,8 @@
+2008-03-05	Till Straumann <strauman@slac.stanford.edu>
+
+	* new-exceptions/bspsupport/ppc_exc_asm_macros.h: bugfix;
+	need to andc with irq mask when disabling interrupts.
+
 2008-02-19	Ralf Corsépius <ralf.corsepius@rtems.org>
 
 	* old-exceptions/README, old-exceptions/TODO, old-exceptions/cpu.c,
diff --git a/c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc_asm_macros.h b/c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc_asm_macros.h
index 04863203dd..5b3a39b456 100644
--- a/c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc_asm_macros.h
+++ b/c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc_asm_macros.h
@@ -92,7 +92,7 @@ no_r1_reload_\FLVR:
 	/* disable interrupts */
 	lwz		\RA, ppc_exc_msr_irq_mask@sdarel(r13)
 	mfmsr	\RB
-	and		\RA, \RB, \RA
+	andc	\RA, \RB, \RA
 	mtmsr	\RA
 	/* increment nest level */
 	lwz		\RA, _ISR_Nest_level@sdarel(r13)