diff --git a/.gitignore b/.gitignore
index 44f269cc..7f2dec23 100644
--- a/.gitignore
+++ b/.gitignore
@@ -62,6 +62,7 @@ coverage
 /tests/test_filter_flags
 /tests/test_hardware
 /tests/test_index
+/tests/test_index_hash
 /test/test_lzip_decoder
 /tests/test_memlimit
 /tests/test_stream_flags
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c4f10594..3a58d740 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -801,6 +801,7 @@ if(BUILD_TESTING)
         test_filter_flags
         test_hardware
         test_index
+        test_index_hash
         test_memlimit
         test_stream_flags
         test_vli
@@ -812,6 +813,7 @@ if(BUILD_TESTING)
         target_include_directories("${TEST}" PRIVATE
             src/common
             src/liblzma/api
+            src/liblzma
             lib
         )
 
diff --git a/src/liblzma/common/index.c b/src/liblzma/common/index.c
index 24ec3c10..97cc9f95 100644
--- a/src/liblzma/common/index.c
+++ b/src/liblzma/common/index.c
@@ -10,6 +10,7 @@
 //
 ///////////////////////////////////////////////////////////////////////////////
 
+#include "common.h"
 #include "index.h"
 #include "stream_flags_common.h"
 
diff --git a/src/liblzma/common/index.h b/src/liblzma/common/index.h
index 64e97247..031efcc7 100644
--- a/src/liblzma/common/index.h
+++ b/src/liblzma/common/index.h
@@ -2,6 +2,13 @@
 //
 /// \file       index.h
 /// \brief      Handling of Index
+/// \note       This header file does not include common.h or lzma.h because
+///             this file is needed by both liblzma internally and by the
+///             tests. Including common.h will include and define many things
+///             the tests do not need and prevents issues with header file
+///             include order. This way, if lzma.h or common.h are not
+///             included before this file it will break on every OS instead
+///             of causing more subtle errors.
 //
 //  Author:     Lasse Collin
 //
@@ -13,8 +20,6 @@
 #ifndef LZMA_INDEX_H
 #define LZMA_INDEX_H
 
-#include "common.h"
-
 
 /// Minimum Unpadded Size
 #define UNPADDED_SIZE_MIN LZMA_VLI_C(5)
@@ -22,6 +27,9 @@
 /// Maximum Unpadded Size
 #define UNPADDED_SIZE_MAX (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
 
+/// Index Indicator based on xz specification
+#define INDEX_INDICATOR 0
+
 
 /// Get the size of the Index Padding field. This is needed by Index encoder
 /// and decoder, but applications should have no use for this.
diff --git a/src/liblzma/common/index_decoder.c b/src/liblzma/common/index_decoder.c
index b2689885..8622b2f0 100644
--- a/src/liblzma/common/index_decoder.c
+++ b/src/liblzma/common/index_decoder.c
@@ -80,7 +80,7 @@ index_decode(void *coder_ptr, const lzma_allocator *allocator,
 		// format". One could argue that the application should
 		// verify the Index Indicator before trying to decode the
 		// Index, but well, I suppose it is simpler this way.
-		if (in[(*in_pos)++] != 0x00)
+		if (in[(*in_pos)++] != INDEX_INDICATOR)
 			return LZMA_DATA_ERROR;
 
 		coder->sequence = SEQ_COUNT;
diff --git a/src/liblzma/common/index_decoder.h b/src/liblzma/common/index_decoder.h
index 1af433b5..3fec4833 100644
--- a/src/liblzma/common/index_decoder.h
+++ b/src/liblzma/common/index_decoder.h
@@ -13,6 +13,7 @@
 #ifndef LZMA_INDEX_DECODER_H
 #define LZMA_INDEX_DECODER_H
 
+#include "common.h"
 #include "index.h"
 
 
diff --git a/src/liblzma/common/index_encoder.c b/src/liblzma/common/index_encoder.c
index ac97d0ce..c7cafb72 100644
--- a/src/liblzma/common/index_encoder.c
+++ b/src/liblzma/common/index_encoder.c
@@ -65,7 +65,7 @@ index_encode(void *coder_ptr,
 	while (*out_pos < out_size)
 	switch (coder->sequence) {
 	case SEQ_INDICATOR:
-		out[*out_pos] = 0x00;
+		out[*out_pos] = INDEX_INDICATOR;
 		++*out_pos;
 		coder->sequence = SEQ_COUNT;
 		break;
diff --git a/src/liblzma/common/index_hash.c b/src/liblzma/common/index_hash.c
index 34df85d7..f55f7bc8 100644
--- a/src/liblzma/common/index_hash.c
+++ b/src/liblzma/common/index_hash.c
@@ -145,7 +145,7 @@ lzma_index_hash_append(lzma_index_hash *index_hash, lzma_vli unpadded_size,
 		lzma_vli uncompressed_size)
 {
 	// Validate the arguments.
-	if (index_hash->sequence != SEQ_BLOCK
+	if (index_hash == NULL || index_hash->sequence != SEQ_BLOCK
 			|| unpadded_size < UNPADDED_SIZE_MIN
 			|| unpadded_size > UNPADDED_SIZE_MAX
 			|| uncompressed_size > LZMA_VLI_MAX)
@@ -190,7 +190,7 @@ lzma_index_hash_decode(lzma_index_hash *index_hash, const uint8_t *in,
 	switch (index_hash->sequence) {
 	case SEQ_BLOCK:
 		// Check the Index Indicator is present.
-		if (in[(*in_pos)++] != 0x00)
+		if (in[(*in_pos)++] != INDEX_INDICATOR)
 			return LZMA_DATA_ERROR;
 
 		index_hash->sequence = SEQ_COUNT;
diff --git a/src/liblzma/common/stream_buffer_encoder.c b/src/liblzma/common/stream_buffer_encoder.c
index af49554a..73157590 100644
--- a/src/liblzma/common/stream_buffer_encoder.c
+++ b/src/liblzma/common/stream_buffer_encoder.c
@@ -10,6 +10,7 @@
 //
 ///////////////////////////////////////////////////////////////////////////////
 
+#include "common.h"
 #include "index.h"
 
 
diff --git a/src/liblzma/common/stream_decoder.c b/src/liblzma/common/stream_decoder.c
index dcf7c149..64283812 100644
--- a/src/liblzma/common/stream_decoder.c
+++ b/src/liblzma/common/stream_decoder.c
@@ -12,6 +12,7 @@
 
 #include "stream_decoder.h"
 #include "block_decoder.h"
+#include "index.h"
 
 
 typedef struct {
@@ -164,7 +165,7 @@ stream_decode(void *coder_ptr, const lzma_allocator *allocator,
 
 		if (coder->pos == 0) {
 			// Detect if it's Index.
-			if (in[*in_pos] == 0x00) {
+			if (in[*in_pos] == INDEX_INDICATOR) {
 				coder->sequence = SEQ_INDEX;
 				break;
 			}
diff --git a/src/liblzma/common/stream_decoder_mt.c b/src/liblzma/common/stream_decoder_mt.c
index 5733c764..fd5cd7fd 100644
--- a/src/liblzma/common/stream_decoder_mt.c
+++ b/src/liblzma/common/stream_decoder_mt.c
@@ -887,7 +887,7 @@ decode_block_header(struct lzma_stream_coder *coder,
 
 	if (coder->pos == 0) {
 		// Detect if it's Index.
-		if (in[*in_pos] == 0x00)
+		if (in[*in_pos] == INDEX_INDICATOR)
 			return LZMA_INDEX_DETECTED;
 
 		// Calculate the size of the Block Header. Note that
diff --git a/tests/Makefile.am b/tests/Makefile.am
index f84c1749..b1a2378a 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -26,6 +26,7 @@ EXTRA_DIST = \
 AM_CPPFLAGS = \
 	-I$(top_srcdir)/src/common \
 	-I$(top_srcdir)/src/liblzma/api \
+	-I$(top_srcdir)/src/liblzma \
 	-I$(top_builddir)/lib
 
 LDADD = $(top_builddir)/src/liblzma/liblzma.la
@@ -44,6 +45,7 @@ check_PROGRAMS = \
 	test_filter_flags \
 	test_block_header \
 	test_index \
+	test_index_hash \
 	test_bcj_exact_size \
 	test_memlimit \
 	test_lzip_decoder \
@@ -56,6 +58,7 @@ TESTS = \
 	test_filter_flags \
 	test_block_header \
 	test_index \
+	test_index_hash \
 	test_bcj_exact_size \
 	test_memlimit \
 	test_lzip_decoder \
diff --git a/tests/test_index_hash.c b/tests/test_index_hash.c
new file mode 100644
index 00000000..2cf91138
--- /dev/null
+++ b/tests/test_index_hash.c
@@ -0,0 +1,388 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       test_index_hash.c
+/// \brief      Tests src/liblzma/common/index_hash.c API functions
+///
+/// \note       No test included for lzma_index_hash_end since it
+///             would be trivial unless tested for memory leaks
+///             with something like valgrind
+//
+//  Author:     Jia Tan
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "tests.h"
+
+// Needed for UNPADDED_SIZE_MIN and UNPADDED_SIZE_MAX macro definitions
+// and index_size and vli_ceil4 helper functions
+#include "common/index.h"
+
+
+static void
+test_lzma_index_hash_init(void)
+{
+#ifndef HAVE_DECODERS
+	assert_skip("Decoder support disabled");
+#else
+	// First test with NULL index_hash.
+	// This should create a fresh index_hash.
+	lzma_index_hash *index_hash = lzma_index_hash_init(NULL, NULL);
+	assert_true(index_hash != NULL);
+
+	// Next test with non-NULL index_hash.
+	lzma_index_hash *second_hash = lzma_index_hash_init(index_hash, NULL);
+
+	// It should not create a new index_hash pointer.
+	// Instead it must just re-init the first index_hash.
+	assert_true(index_hash == second_hash);
+
+	lzma_index_hash_end(index_hash, NULL);
+#endif
+}
+
+
+static void
+test_lzma_index_hash_append(void)
+{
+#ifndef HAVE_DECODERS
+	assert_skip("Decoder support disabled");
+#else
+	// Test all invalid parameters
+	assert_lzma_ret(lzma_index_hash_append(NULL, 0, 0),
+			LZMA_PROG_ERROR);
+
+	// Test NULL index_hash
+	assert_lzma_ret(lzma_index_hash_append(NULL, UNPADDED_SIZE_MIN,
+			LZMA_VLI_MAX), LZMA_PROG_ERROR);
+
+	// Test with invalid Unpadded Size
+	lzma_index_hash *index_hash = lzma_index_hash_init(NULL, NULL);
+	assert_true(index_hash != NULL);
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			UNPADDED_SIZE_MIN - 1, LZMA_VLI_MAX),
+			LZMA_PROG_ERROR);
+
+	// Test with invalid Uncompressed Size
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			UNPADDED_SIZE_MIN, LZMA_VLI_MAX + 1),
+			LZMA_PROG_ERROR);
+
+	// First append a Record describing a small Block.
+	// This should succeed.
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			UNPADDED_SIZE_MIN, 1), LZMA_OK);
+
+	// Append another small Record.
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			UNPADDED_SIZE_MIN, 1), LZMA_OK);
+
+	// Append a Record that would cause the compressed size to grow
+	// too big
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			UNPADDED_SIZE_MAX, 1), LZMA_DATA_ERROR);
+
+	lzma_index_hash_end(index_hash, NULL);
+#endif
+}
+
+
+#ifdef HAVE_DECODERS
+// Fill an index_hash with unpadded and uncompressed VLIs
+// by calling lzma_index_hash_append
+static void
+fill_index_hash(lzma_index_hash *index_hash, const lzma_vli *unpadded_sizes,
+		const lzma_vli *uncomp_sizes, uint32_t block_count)
+{
+	for (uint32_t i = 0; i < block_count; ++i)
+		assert_lzma_ret(lzma_index_hash_append(index_hash,
+			unpadded_sizes[i], uncomp_sizes[i]), LZMA_OK);
+}
+
+
+#ifdef HAVE_ENCODERS
+// Set the contents of buf to the expected Index based on the
+// .xz specification. This needs the unpadded and uncompressed VLIs
+// to correctly create the Index.
+static void
+generate_index(uint8_t *buf, const lzma_vli *unpadded_sizes,
+		const lzma_vli *uncomp_sizes, uint32_t block_count,
+		size_t index_max_size)
+{
+	size_t in_pos = 0;
+	size_t out_pos = 0;
+
+	// First set Index Indicator
+	buf[out_pos++] = INDEX_INDICATOR;
+
+	// Next write out Number of Records
+	assert_lzma_ret(lzma_vli_encode(block_count, &in_pos, buf,
+			&out_pos, index_max_size), LZMA_STREAM_END);
+
+	// Next write out each Record.
+	// A Record consists of Unpadded Size and Uncompressed Size
+	// written next to each other as VLIs.
+	for (uint32_t i = 0; i < block_count; ++i) {
+		in_pos = 0;
+		assert_lzma_ret(lzma_vli_encode(unpadded_sizes[i], &in_pos,
+			buf, &out_pos, index_max_size), LZMA_STREAM_END);
+		in_pos = 0;
+		assert_lzma_ret(lzma_vli_encode(uncomp_sizes[i], &in_pos,
+			buf, &out_pos, index_max_size), LZMA_STREAM_END);
+	}
+
+	// Add Index Padding
+	lzma_vli rounded_out_pos = vli_ceil4(out_pos);
+	memzero(buf + out_pos, rounded_out_pos - out_pos);
+	out_pos = rounded_out_pos;
+
+	// Add the CRC32
+	write32le(buf + out_pos, lzma_crc32(buf, out_pos, 0));
+	out_pos += 4;
+
+	assert_uint_eq(out_pos, index_max_size);
+}
+#endif
+#endif
+
+
+static void
+test_lzma_index_hash_decode(void)
+{
+#if !defined(HAVE_ENCODERS) || !defined(HAVE_DECODERS)
+	assert_skip("Encoder or decoder support disabled");
+#else
+	lzma_index_hash *index_hash = lzma_index_hash_init(NULL, NULL);
+	assert_true(index_hash != NULL);
+
+	size_t in_pos = 0;
+
+	// Six valid values for the Unpadded Size fields in an Index
+	const lzma_vli unpadded_sizes[6] = {
+		UNPADDED_SIZE_MIN,
+		1000,
+		4000,
+		8000,
+		16000,
+		32000
+	};
+
+	// Six valid values for the Uncompressed Size fields in an Index
+	const lzma_vli uncomp_sizes[6] = {
+		1,
+		500,
+		8000,
+		20,
+		1,
+		500
+	};
+
+	// Add two Records to an index_hash
+	fill_index_hash(index_hash, unpadded_sizes, uncomp_sizes, 2);
+
+	const lzma_vli size_two_records = lzma_index_hash_size(index_hash);
+	assert_uint(size_two_records, >, 0);
+	uint8_t *index_two_records = tuktest_malloc(size_two_records);
+
+	generate_index(index_two_records, unpadded_sizes, uncomp_sizes, 2,
+			size_two_records);
+
+	// First test for basic buffer size error
+	in_pos = size_two_records + 1;
+	assert_lzma_ret(lzma_index_hash_decode(index_hash,
+			index_two_records, &in_pos,
+			size_two_records), LZMA_BUF_ERROR);
+
+	// Next test for invalid Index Indicator
+	in_pos = 0;
+	index_two_records[0] ^= 1;
+	assert_lzma_ret(lzma_index_hash_decode(index_hash,
+			index_two_records, &in_pos,
+			size_two_records), LZMA_DATA_ERROR);
+	index_two_records[0] ^= 1;
+
+	// Next verify the index_hash as expected
+	in_pos = 0;
+	assert_lzma_ret(lzma_index_hash_decode(index_hash,
+			index_two_records, &in_pos,
+			size_two_records), LZMA_STREAM_END);
+
+	// Next test an index_hash with three Records
+	index_hash = lzma_index_hash_init(index_hash, NULL);
+	fill_index_hash(index_hash, unpadded_sizes, uncomp_sizes, 3);
+
+	const lzma_vli size_three_records = lzma_index_hash_size(
+			index_hash);
+	assert_uint(size_three_records, >, 0);
+	uint8_t *index_three_records = tuktest_malloc(size_three_records);
+
+	generate_index(index_three_records, unpadded_sizes, uncomp_sizes,
+			3, size_three_records);
+
+	in_pos = 0;
+	assert_lzma_ret(lzma_index_hash_decode(index_hash,
+			index_three_records, &in_pos,
+			size_three_records), LZMA_STREAM_END);
+
+	// Next test an index_hash with five Records
+	index_hash = lzma_index_hash_init(index_hash, NULL);
+	fill_index_hash(index_hash, unpadded_sizes, uncomp_sizes, 5);
+
+	const lzma_vli size_five_records = lzma_index_hash_size(
+			index_hash);
+	assert_uint(size_five_records, >, 0);
+	uint8_t *index_five_records = tuktest_malloc(size_five_records);
+
+	generate_index(index_five_records, unpadded_sizes, uncomp_sizes, 5,
+			size_five_records);
+
+	// Instead of testing all input at once, give input
+	// one byte at a time
+	in_pos = 0;
+	for (lzma_vli i = 0; i < size_five_records - 1; ++i) {
+		assert_lzma_ret(lzma_index_hash_decode(index_hash,
+				index_five_records, &in_pos, in_pos + 1),
+				LZMA_OK);
+	}
+
+	// Last byte should return LZMA_STREAM_END
+	assert_lzma_ret(lzma_index_hash_decode(index_hash,
+			index_five_records, &in_pos,
+			in_pos + 1), LZMA_STREAM_END);
+
+	// Next test if the index_hash is given an incorrect Unpadded
+	// Size. Should detect and report LZMA_DATA_ERROR
+	index_hash = lzma_index_hash_init(index_hash, NULL);
+	fill_index_hash(index_hash, unpadded_sizes, uncomp_sizes, 5);
+	// The sixth Record will have an invalid Unpadded Size
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			unpadded_sizes[5] + 1,
+			uncomp_sizes[5]), LZMA_OK);
+
+	const lzma_vli size_six_records = lzma_index_hash_size(
+			index_hash);
+
+	assert_uint(size_six_records, >, 0);
+	uint8_t *index_six_records = tuktest_malloc(size_six_records);
+
+	generate_index(index_six_records, unpadded_sizes, uncomp_sizes, 6,
+			size_six_records);
+	in_pos = 0;
+	assert_lzma_ret(lzma_index_hash_decode(index_hash,
+			index_six_records, &in_pos,
+			size_six_records), LZMA_DATA_ERROR);
+
+	// Next test if the Index is corrupt (invalid CRC32).
+	// Should detect and report LZMA_DATA_ERROR
+	index_hash = lzma_index_hash_init(index_hash, NULL);
+	fill_index_hash(index_hash, unpadded_sizes, uncomp_sizes, 2);
+
+	index_two_records[size_two_records - 1] ^= 1;
+
+	in_pos = 0;
+	assert_lzma_ret(lzma_index_hash_decode(index_hash,
+			index_two_records, &in_pos,
+			size_two_records), LZMA_DATA_ERROR);
+
+	// Next test with Index and index_hash struct not matching
+	// a Record
+	index_hash = lzma_index_hash_init(index_hash, NULL);
+	fill_index_hash(index_hash, unpadded_sizes, uncomp_sizes, 2);
+	// Recalculate Index with invalid Unpadded Size
+	const lzma_vli unpadded_sizes_invalid[2] = {
+		unpadded_sizes[0],
+		unpadded_sizes[1] + 1
+	};
+
+	generate_index(index_two_records, unpadded_sizes_invalid,
+			uncomp_sizes, 2, size_two_records);
+
+	in_pos = 0;
+	assert_lzma_ret(lzma_index_hash_decode(index_hash,
+			index_two_records, &in_pos,
+			size_two_records), LZMA_DATA_ERROR);
+
+	lzma_index_hash_end(index_hash, NULL);
+#endif
+}
+
+
+static void
+test_lzma_index_hash_size(void)
+{
+#ifndef HAVE_DECODERS
+	assert_skip("Decoder support disabled");
+#else
+	lzma_index_hash *index_hash = lzma_index_hash_init(NULL, NULL);
+	assert_true(index_hash != NULL);
+
+	// First test empty index_hash
+	// Expected size should be:
+	// Index Indicator - 1 byte
+	// Number of Records - 1 byte
+	// List of Records - 0 bytes
+	// Index Padding - 2 bytes
+	// CRC32 - 4 bytes
+	// Total - 8 bytes
+	assert_uint_eq(lzma_index_hash_size(index_hash), 8);
+
+	// Append a Record describing a small Block to the index_hash
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			UNPADDED_SIZE_MIN, 1), LZMA_OK);
+
+	// Expected size should be:
+	// Index Indicator - 1 byte
+	// Number of Records - 1 byte
+	// List of Records - 2 bytes
+	// Index Padding - 0 bytes
+	// CRC32 - 4 bytes
+	// Total - 8 bytes
+	lzma_vli expected_size = 8;
+	assert_uint_eq(lzma_index_hash_size(index_hash), expected_size);
+
+	// Append additional small Record
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			UNPADDED_SIZE_MIN, 1), LZMA_OK);
+
+	// Expected size should be:
+	// Index Indicator - 1 byte
+	// Number of Records - 1 byte
+	// List of Records - 4 bytes
+	// Index Padding - 2 bytes
+	// CRC32 - 4 bytes
+	// Total - 12 bytes
+	expected_size = 12;
+	assert_uint_eq(lzma_index_hash_size(index_hash), expected_size);
+
+	// Append a larger Record to the index_hash (3 bytes for each VLI)
+	const lzma_vli three_byte_vli = 0x10000;
+	assert_lzma_ret(lzma_index_hash_append(index_hash,
+			three_byte_vli, three_byte_vli), LZMA_OK);
+
+	// Expected size should be:
+	// Index Indicator - 1 byte
+	// Number of Records - 1 byte
+	// List of Records - 10 bytes
+	// Index Padding - 0 bytes
+	// CRC32 - 4 bytes
+	// Total - 16 bytes
+	expected_size = 16;
+	assert_uint_eq(lzma_index_hash_size(index_hash), expected_size);
+
+	lzma_index_hash_end(index_hash, NULL);
+#endif
+}
+
+
+extern int
+main(int argc, char **argv)
+{
+	tuktest_start(argc, argv);
+	tuktest_run(test_lzma_index_hash_init);
+	tuktest_run(test_lzma_index_hash_append);
+	tuktest_run(test_lzma_index_hash_decode);
+	tuktest_run(test_lzma_index_hash_size);
+	return tuktest_end();
+}