diff --git a/Tests/test_file_libtiff.py b/Tests/test_file_libtiff.py
index 58a3d38c5..19c952ae4 100644
--- a/Tests/test_file_libtiff.py
+++ b/Tests/test_file_libtiff.py
@@ -231,6 +231,24 @@ class TestFileLibTiff(LibTiffTestCase):
 
         TiffImagePlugin.WRITE_LIBTIFF = False
 
+    def test_custom_metadata(self):
+        custom = {
+            37000: 4,
+            37001: 4.2
+        }
+        for libtiff in [False, True]:
+            TiffImagePlugin.WRITE_LIBTIFF = libtiff
+
+            im = hopper()
+
+            out = self.tempfile("temp.tif")
+            im.save(out, tiffinfo=custom)
+            TiffImagePlugin.WRITE_LIBTIFF = False
+
+            reloaded = Image.open(out)
+            for tag, value in custom.items():
+                self.assertEqual(reloaded.tag_v2[tag], value)
+
     def test_int_dpi(self):
         # issue #1765
         im = hopper('RGB')
diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
index 5059a1324..c2b09e294 100644
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -1499,11 +1499,10 @@ def _save(im, fp, filename):
                                           getattr(im, 'tag_v2', {}).items(),
                                           legacy_ifd.items()):
             # Libtiff can only process certain core items without adding
-            # them to the custom dictionary. It will segfault if it attempts
-            # to add a custom tag without the dictionary entry
-            #
-            # UNDONE --  add code for the custom dictionary
-            if tag not in TiffTags.LIBTIFF_CORE:
+            # them to the custom dictionary. Support has only been been added
+            # for int and float values
+            if tag not in TiffTags.LIBTIFF_CORE and not \
+               (isinstance(value, int) or isinstance(value, float)):
                 continue
             if tag not in atts and tag not in blocklist:
                 if isinstance(value, str if py3 else unicode):
diff --git a/src/PIL/TiffTags.py b/src/PIL/TiffTags.py
index c1e14af4a..d810f2f35 100644
--- a/src/PIL/TiffTags.py
+++ b/src/PIL/TiffTags.py
@@ -425,6 +425,7 @@ TYPES = {}
 
 # some of these are not in our TAGS_V2 dict and were included from tiff.h
 
+# This list also exists in encode.c
 LIBTIFF_CORE = {255, 256, 257, 258, 259, 262, 263, 266, 274, 277,
                 278, 280, 281, 340, 341, 282, 283, 284, 286, 287,
                 296, 297, 321, 320, 338, 32995, 322, 323, 32998,
diff --git a/src/encode.c b/src/encode.c
index c60048c41..385d576dd 100644
--- a/src/encode.c
+++ b/src/encode.c
@@ -804,7 +804,13 @@ PyImaging_LibTiffEncoderNew(PyObject* self, PyObject* args)
     PyObject *dir;
     PyObject *key, *value;
     Py_ssize_t pos = 0;
-    int status;
+    int key_int, status, is_core_tag, i;
+    // This list also exists in TiffTags.py
+    const int tags[32] = {
+        256, 257, 258, 259, 262, 263, 266, 269, 274, 277, 278, 280, 281, 340,
+        341, 282, 283, 284, 286, 287, 296, 297, 321, 338, 32995, 32998, 32996,
+        339, 32997, 330, 531, 530
+    };
 
     Py_ssize_t d_size;
     PyObject *keys, *values;
@@ -845,21 +851,33 @@ PyImaging_LibTiffEncoderNew(PyObject* self, PyObject* args)
 
     for (pos = 0; pos < d_size; pos++) {
         key = PyList_GetItem(keys, pos);
+        key_int = (int)PyInt_AsLong(key);
         value = PyList_GetItem(values, pos);
         status = 0;
-        TRACE(("Attempting to set key: %d\n", (int)PyInt_AsLong(key)));
+        is_core_tag = 0;
+        for (i=0; i<32; i++) {
+            if (tags[i] == key_int) {
+                is_core_tag = 1;
+                break;
+            }
+        }
+        TRACE(("Attempting to set key: %d\n", key_int));
         if (PyInt_Check(value)) {
-            TRACE(("Setting from Int: %d %ld \n", (int)PyInt_AsLong(key),PyInt_AsLong(value)));
-            status = ImagingLibTiffSetField(&encoder->state,
-                                            (ttag_t) PyInt_AsLong(key),
-                                            PyInt_AsLong(value));
+            TRACE(("Setting from Int: %d %ld \n", key_int, PyInt_AsLong(value)));
+            if (is_core_tag || !ImagingLibTiffMergeFieldInfo(&encoder->state, TIFF_LONG, key_int)) {
+                status = ImagingLibTiffSetField(&encoder->state,
+                                                (ttag_t) PyInt_AsLong(key),
+                                                PyInt_AsLong(value));
+            }
         } else if (PyFloat_Check(value)) {
-            TRACE(("Setting from Float: %d, %f \n", (int)PyInt_AsLong(key),PyFloat_AsDouble(value)));
-            status = ImagingLibTiffSetField(&encoder->state,
-                                            (ttag_t) PyInt_AsLong(key),
-                                            (float)PyFloat_AsDouble(value));
+            TRACE(("Setting from Float: %d, %f \n", key_int, PyFloat_AsDouble(value)));
+            if (is_core_tag || !ImagingLibTiffMergeFieldInfo(&encoder->state, TIFF_DOUBLE, key_int)) {
+                status = ImagingLibTiffSetField(&encoder->state,
+                                                (ttag_t) PyInt_AsLong(key),
+                                                (double)PyFloat_AsDouble(value));
+            }
         } else if (PyBytes_Check(value)) {
-            TRACE(("Setting from Bytes: %d, %s \n", (int)PyInt_AsLong(key),PyBytes_AsString(value)));
+            TRACE(("Setting from Bytes: %d, %s \n", key_int, PyBytes_AsString(value)));
             status = ImagingLibTiffSetField(&encoder->state,
                                             (ttag_t) PyInt_AsLong(key),
                                             PyBytes_AsString(value));
@@ -867,7 +885,7 @@ PyImaging_LibTiffEncoderNew(PyObject* self, PyObject* args)
             Py_ssize_t len,i;
             float *floatav;
             int *intav;
-            TRACE(("Setting from Tuple: %d \n", (int)PyInt_AsLong(key)));
+            TRACE(("Setting from Tuple: %d \n", key_int));
             len = PyTuple_Size(value);
             if (len) {
                 if (PyInt_Check(PyTuple_GetItem(value,0))) {
@@ -898,13 +916,13 @@ PyImaging_LibTiffEncoderNew(PyObject* self, PyObject* args)
                     }
                 } else {
                     TRACE(("Unhandled type in tuple for key %d : %s \n",
-                           (int)PyInt_AsLong(key),
+                           key_int,
                            PyBytes_AsString(PyObject_Str(value))));
                 }
             }
         } else {
             TRACE(("Unhandled type for key %d : %s \n",
-                   (int)PyInt_AsLong(key),
+                   key_int,
                    PyBytes_AsString(PyObject_Str(value))));
         }
         if (!status) {
diff --git a/src/libImaging/TiffDecode.c b/src/libImaging/TiffDecode.c
index e77afdf61..bfab4b79e 100644
--- a/src/libImaging/TiffDecode.c
+++ b/src/libImaging/TiffDecode.c
@@ -402,6 +402,19 @@ int ImagingLibTiffEncodeInit(ImagingCodecState state, char *filename, int fp) {
 
 }
 
+int ImagingLibTiffMergeFieldInfo(ImagingCodecState state, TIFFDataType field_type, int key){
+    TIFFSTATE *clientstate = (TIFFSTATE *)state->context;
+    char field_name[10];
+    uint32 n;
+
+    const TIFFFieldInfo info[] = {
+        { key, 0, 1, field_type, FIELD_CUSTOM, 1, 0, field_name }
+    };
+    n = sizeof(info) / sizeof(info[0]);
+
+    return TIFFMergeFieldInfo(clientstate->tiff, info, n);
+}
+
 int ImagingLibTiffSetField(ImagingCodecState state, ttag_t tag, ...){
     // after tif_dir.c->TIFFSetField.
     TIFFSTATE *clientstate = (TIFFSTATE *)state->context;
diff --git a/src/libImaging/TiffDecode.h b/src/libImaging/TiffDecode.h
index e14a09329..e29a6c88f 100644
--- a/src/libImaging/TiffDecode.h
+++ b/src/libImaging/TiffDecode.h
@@ -45,6 +45,7 @@ typedef struct {
 
 extern int ImagingLibTiffInit(ImagingCodecState state, int fp, int offset);
 extern int ImagingLibTiffEncodeInit(ImagingCodecState state, char *filename, int fp);
+extern int ImagingLibTiffMergeFieldInfo(ImagingCodecState state, TIFFDataType field_type, int key);
 extern int ImagingLibTiffSetField(ImagingCodecState state, ttag_t tag, ...);