diff --git a/Tests/test_lib_pack.py b/Tests/test_lib_pack.py
index e0fcf264a..635b5679a 100644
--- a/Tests/test_lib_pack.py
+++ b/Tests/test_lib_pack.py
@@ -309,13 +309,25 @@ class TestLibUnpack(PillowTestCase):
             "RGBA", "LA;16B", 4, (1, 1, 1, 3), (5, 5, 5, 7), (9, 9, 9, 11))
         self.assert_unpack(
             "RGBA", "RGBA", 4, (1, 2, 3, 4), (5, 6, 7, 8), (9, 10, 11, 12))
+        self.assert_unpack(
+            "RGBA", "RGBAX", 5, (1, 2, 3, 4), (6, 7, 8, 9), (11, 12, 13, 14))
+        self.assert_unpack(
+            "RGBA", "RGBAXX", 6, (1, 2, 3, 4), (7, 8, 9, 10), (13, 14, 15, 16))
         self.assert_unpack(
             "RGBA", "RGBa", 4,
             (63, 127, 191, 4), (159, 191, 223, 8), (191, 212, 233, 12))
         self.assert_unpack(
             "RGBA", "RGBa",
-            b'\x01\x02\x03\x00\x10\x20\x30\xff',
-            (0, 0, 0, 0), (16, 32, 48, 255))
+            b'\x01\x02\x03\x00\x10\x20\x30\x7f\x10\x20\x30\xff',
+            (0, 0, 0, 0), (32, 64, 96, 127), (16, 32, 48, 255))
+        self.assert_unpack(
+            "RGBA", "RGBaX",
+            b'\x01\x02\x03\x00-\x10\x20\x30\x7f-\x10\x20\x30\xff-',
+            (0, 0, 0, 0), (32, 64, 96, 127), (16, 32, 48, 255))
+        self.assert_unpack(
+            "RGBA", "RGBaXX",
+            b'\x01\x02\x03\x00==\x10\x20\x30\x7f!!\x10\x20\x30\xff??',
+            (0, 0, 0, 0), (32, 64, 96, 127), (16, 32, 48, 255))
         self.assert_unpack(
             "RGBA", "RGBa;16L", 8,
             (63, 127, 191, 8), (159, 191, 223, 16), (191, 212, 233, 24))
diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
index c1a785ef3..413dc3943 100644
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -207,8 +207,16 @@ OPEN_INFO = {
     (MM, 2, (1,), 1, (8, 8, 8, 8, 8, 8), (0, 0, 0)): ("RGBX", "RGBXXX"),
     (II, 2, (1,), 1, (8, 8, 8, 8), (1,)): ("RGBA", "RGBa"),
     (MM, 2, (1,), 1, (8, 8, 8, 8), (1,)): ("RGBA", "RGBa"),
+    (II, 2, (1,), 1, (8, 8, 8, 8, 8), (1, 0)): ("RGBA", "RGBaX"),
+    (MM, 2, (1,), 1, (8, 8, 8, 8, 8), (1, 0)): ("RGBA", "RGBaX"),
+    (II, 2, (1,), 1, (8, 8, 8, 8, 8, 8), (1, 0, 0)): ("RGBA", "RGBaXX"),
+    (MM, 2, (1,), 1, (8, 8, 8, 8, 8, 8), (1, 0, 0)): ("RGBA", "RGBaXX"),
     (II, 2, (1,), 1, (8, 8, 8, 8), (2,)): ("RGBA", "RGBA"),
     (MM, 2, (1,), 1, (8, 8, 8, 8), (2,)): ("RGBA", "RGBA"),
+    (II, 2, (1,), 1, (8, 8, 8, 8, 8), (2, 0)): ("RGBA", "RGBAX"),
+    (MM, 2, (1,), 1, (8, 8, 8, 8, 8), (2, 0)): ("RGBA", "RGBAX"),
+    (II, 2, (1,), 1, (8, 8, 8, 8, 8, 8), (2, 0, 0)): ("RGBA", "RGBAXX"),
+    (MM, 2, (1,), 1, (8, 8, 8, 8, 8, 8), (2, 0, 0)): ("RGBA", "RGBAXX"),
     (II, 2, (1,), 1, (8, 8, 8, 8), (999,)): ("RGBA", "RGBA"),  # Corel Draw 10
     (MM, 2, (1,), 1, (8, 8, 8, 8), (999,)): ("RGBA", "RGBA"),  # Corel Draw 10
 
@@ -253,8 +261,8 @@ OPEN_INFO = {
     (MM, 6, (1,), 1, (8, 8, 8), ()): ("YCbCr", "YCbCr"),
     (II, 6, (1,), 1, (8, 8, 8, 8), (0,)): ("YCbCr", "YCbCrX"),
     (MM, 6, (1,), 1, (8, 8, 8, 8), (0,)): ("YCbCr", "YCbCrX"),
-    (II, 6, (1,), 1, (8, 8, 8, 8, 8), (0, 0)): ("YCbCr", "YCbCrXXX"),
-    (MM, 6, (1,), 1, (8, 8, 8, 8, 8), (0, 0)): ("YCbCr", "YCbCrXXX"),
+    (II, 6, (1,), 1, (8, 8, 8, 8, 8), (0, 0)): ("YCbCr", "YCbCrXX"),
+    (MM, 6, (1,), 1, (8, 8, 8, 8, 8), (0, 0)): ("YCbCr", "YCbCrXX"),
     (II, 6, (1,), 1, (8, 8, 8, 8, 8, 8), (0, 0, 0)): ("YCbCr", "YCbCrXXX"),
     (MM, 6, (1,), 1, (8, 8, 8, 8, 8, 8), (0, 0, 0)): ("YCbCr", "YCbCrXXX"),
 
diff --git a/src/libImaging/Unpack.c b/src/libImaging/Unpack.c
index 05b4299b0..7bb8064ee 100644
--- a/src/libImaging/Unpack.c
+++ b/src/libImaging/Unpack.c
@@ -797,6 +797,48 @@ unpackRGBa(UINT8* _out, const UINT8* in, int pixels)
     }
 }
 
+static void
+unpackRGBaskip1(UINT8* _out, const UINT8* in, int pixels)
+{
+    int i;
+    UINT32* out = (UINT32*) _out;
+    /* premultiplied RGBA */
+    for (i = 0; i < pixels; i++) {
+        int a = in[3];
+        if ( ! a) {
+            out[i] = 0;
+        } else if (a == 255) {
+            out[i] = MAKE_UINT32(in[0], in[1], in[2], a);
+        } else {
+            out[i] = MAKE_UINT32(CLIP8(in[0] * 255 / a),
+                                 CLIP8(in[1] * 255 / a),
+                                 CLIP8(in[2] * 255 / a), a);
+        }
+        in += 5;
+    }
+}
+
+static void
+unpackRGBaskip2(UINT8* _out, const UINT8* in, int pixels)
+{
+    int i;
+    UINT32* out = (UINT32*) _out;
+    /* premultiplied RGBA */
+    for (i = 0; i < pixels; i++) {
+        int a = in[3];
+        if ( ! a) {
+            out[i] = 0;
+        } else if (a == 255) {
+            out[i] = MAKE_UINT32(in[0], in[1], in[2], a);
+        } else {
+            out[i] = MAKE_UINT32(CLIP8(in[0] * 255 / a),
+                                 CLIP8(in[1] * 255 / a),
+                                 CLIP8(in[2] * 255 / a), a);
+        }
+        in += 6;
+    }
+}
+
 static void
 unpackBGRa(UINT8* _out, const UINT8* in, int pixels)
 {
@@ -1301,7 +1343,11 @@ static struct {
     {"RGBA",    "LA",           16,     unpackRGBALA},
     {"RGBA",    "LA;16B",       32,     unpackRGBALA16B},
     {"RGBA",    "RGBA",         32,     copy4},
+    {"RGBA",    "RGBAX",        40,     copy4skip1},
+    {"RGBA",    "RGBAXX",       48,     copy4skip2},
     {"RGBA",    "RGBa",         32,     unpackRGBa},
+    {"RGBA",    "RGBaX",        40,     unpackRGBaskip1},
+    {"RGBA",    "RGBaXX",       48,     unpackRGBaskip2},
     {"RGBA",    "RGBa;16L",     64,     unpackRGBa16L},
     {"RGBA",    "RGBa;16B",     64,     unpackRGBa16B},
     {"RGBA",    "BGRa",         32,     unpackBGRa},