diff --git a/xpcom/tests/Makefile.in b/xpcom/tests/Makefile.in
index 225dbde223f..89ef47d591b 100644
--- a/xpcom/tests/Makefile.in
+++ b/xpcom/tests/Makefile.in
@@ -117,17 +117,15 @@ CPP_UNIT_TESTS += \
 endif
 
 ifdef MOZ_DEBUG
-# FIXME bug 456272: testing assertion failures is fragile,
-# and TestDeadlockDetector doesn't like Windows
-ifneq ($(OS_ARCH), WINNT)
-ifneq ($(OS_ARCH), WINCE)
+# FIXME bug 523392: TestDeadlockDetector doesn't like Windows
+# FIXME bug 523378: also fails on OS X
+ifneq (,$(filter-out WINNT WINCE Darwin,$(OS_ARCH)))
 CPP_UNIT_TESTS += \
                   TestDeadlockDetector.cpp \
                   TestDeadlockDetectorScalability.cpp \
                   $(NULL)
 endif
 endif
-endif
 
 ifndef MOZILLA_INTERNAL_API
 CPP_UNIT_TESTS += \