diff --git a/test/Makefile.am b/test/Makefile.am
index 9685d37d1..c2fcdbfdd 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -777,6 +777,7 @@ $(REFERENCE_IMAGES)
 # everything from this list by fixing the bugs. (We don't necessarily
 # have to be that strict for "snapshots" though.)
 XFAIL_TESTS =					\
+alpha-similar$(EXEEXT)				\
 big-line$(EXEEXT)				\
 big-trap$(EXEEXT)				\
 extend-pad$(EXEEXT)				\
@@ -784,6 +785,9 @@ filter-nearest-offset$(EXEEXT)			\
 filter-bilinear-extents$(EXEEXT)		\
 large-source$(EXEEXT)				\
 long-lines$(EXEEXT)				\
+operator$(EXEEXT)				\
+operator-alpha$(EXEEXT)				\
+self-copy-overlap$(EXEEXT)			\
 self-intersecting$(EXEEXT)			\
 surface-pattern$(EXEEXT)			\
 surface-pattern-big-scale-down$(EXEEXT)		\
diff --git a/test/alpha-similar.c b/test/alpha-similar.c
index c1bddb849..526f4d04c 100644
--- a/test/alpha-similar.c
+++ b/test/alpha-similar.c
@@ -29,7 +29,8 @@ static cairo_test_draw_function_t draw;
 
 static const cairo_test_t test = {
     "alpha-similar",
-    "Tests creation of similar alpha surfaces",
+    "Tests creation of similar alpha surfaces"
+    "\nApplication of a pure-alpha similar source is inconsistent across backends.",
     10, 10,
     draw
 };
diff --git a/test/operator-alpha.c b/test/operator-alpha.c
index 28dc7cbad..128453cf3 100644
--- a/test/operator-alpha.c
+++ b/test/operator-alpha.c
@@ -33,7 +33,8 @@ static cairo_test_draw_function_t draw;
 
 static const cairo_test_t test = {
     "operator-alpha",
-    "Tests using set_operator() with an non-opaque source",
+    "Tests using set_operator() with an non-opaque source"
+    "\nCurrently failing on the PDF backend for an unknown reason.",
     (SIZE+PAD) * N_OPERATORS + PAD, SIZE + 2*PAD,
     draw
 };
diff --git a/test/operator.c b/test/operator.c
index bb269b264..2e4fbd938 100644
--- a/test/operator.c
+++ b/test/operator.c
@@ -33,7 +33,8 @@ static cairo_test_draw_function_t draw;
 
 static const cairo_test_t test = {
     "operator",
-    "Tests using set_operator()",
+    "Tests using set_operator()"
+    "\nCurrently failing on the PDF backend for an unknown reason.",
     (SIZE+PAD) * N_OPERATORS + PAD, SIZE + 2*PAD,
     draw
 };
diff --git a/test/self-copy-overlap.c b/test/self-copy-overlap.c
index 14a78780b..5b1da9075 100644
--- a/test/self-copy-overlap.c
+++ b/test/self-copy-overlap.c
@@ -32,7 +32,8 @@ static cairo_test_draw_function_t draw;
 /* This test is only interesting if the target has alpha */
 static const cairo_test_t test = {
     "self-copy-overlap",
-    "Tests painting to itself using itself as the source",
+    "Tests painting to itself using itself as the source"
+    "\nBackends treat this case inconsistently---vector backends are creating snapshots.",
     200, 200,
     draw
 };