diff --git a/ext/bz2/bz2.c b/ext/bz2/bz2.c
index a8153d7d119..91e694f58f4 100644
--- a/ext/bz2/bz2.c
+++ b/ext/bz2/bz2.c
@@ -537,18 +537,17 @@ PHP_FUNCTION(bzdecompress)
 	while ((error = BZ2_bzDecompress(&bzs)) == BZ_OK && bzs.avail_in > 0) {
 		/* compression is better then 2:1, need to allocate more memory */
 		bzs.avail_out = source_len;
-		size = (bzs.total_out_hi32 * (unsigned int) -1) + bzs.total_out_lo32;
+		size = (((uint64_t) bzs.total_out_hi32) << 32U) + bzs.total_out_lo32;
 		if (UNEXPECTED(size > SIZE_MAX)) {
 			/* no reason to continue if we're going to drop it anyway */
 			break;
 		}
-
 		dest = zend_string_safe_realloc(dest, 1, bzs.avail_out+1, (size_t) size, 0);
 		bzs.next_out = ZSTR_VAL(dest) + size;
 	}
 
 	if (error == BZ_STREAM_END || error == BZ_OK) {
-		size = (bzs.total_out_hi32 * (unsigned int) -1) + bzs.total_out_lo32;
+		size = (((uint64_t) bzs.total_out_hi32) << 32U) + bzs.total_out_lo32;
 		if (UNEXPECTED(size > SIZE_MAX)) {
 			php_error_docref(NULL, E_WARNING, "Decompressed size too big, max is %zu", SIZE_MAX);
 			zend_string_efree(dest);
diff --git a/ext/bz2/tests/gh20807.phpt b/ext/bz2/tests/gh20807.phpt
new file mode 100644
index 00000000000..8d1e0cb40e4
--- /dev/null
+++ b/ext/bz2/tests/gh20807.phpt
@@ -0,0 +1,19 @@
+--TEST--
+Truncation of total output size causing erroneous size and data
+--EXTENSIONS--
+bz2
+--INI--
+memory_limit=-1
+--SKIPIF--
+<?php
+if (!getenv('RUN_RESOURCE_HEAVY_TESTS')) die('skip resource-heavy test');
+if (getenv("SKIP_SLOW_TESTS")) die('skip slow test');
+if (PHP_OS === 'FreeBSD') die('skip Worker does not handle OOM gracefully');
+if (PHP_INT_SIZE !== 8) die('skip Only for 64-bit systems');
+?>
+--FILE--
+<?php
+var_dump(sha1(bzdecompress(base64_decode("QlpoOTFBWSZTWei3pg8BX44IAMAAAAggADCATUZCoCWpCoCXMUFZJlNZ6LemDwFfjggAwAAACCAAMIBNRkKgJakKgJcxQVkmU1not6YPAV+OCADAAAAIIAAwgE1GQqAlqQqAlzFBWSZTWei3pg8BX44IAMAAAAggADCATUZCoCWpCoCXMUFZJlNZ6LemDwFfjggAwAAACCAAMIBNRkKgJakKgJcxQVkmU1not6YPAV+OCADAAAAIIAAwgE1GQqAlqQqAlzFBWSZTWei3pg8BX44IAMAAAAggADCATUZCoCWpCoCXMUFZJlNZ6LemDwFfjggAwAAACCAAMIBNRkKgJakKgJcxQVkmU1not6YPAV+OCADAAAAIIAAwgE1GQqAlqQqAlzFBWSZTWei3pg8BX44IAMAAAAggADCATUZCoCWpCoCXMUFZJlNZ6LemDwFfjggAwAAACCAAMIBNRkKgJakKgJcxQVkmU1not6YPAV+OCADAAAAIIAAwgE1GQqAlqQqAlzFBWSZTWei3pg8BX44IAMAAAAggADCATUZCoCWpCoCXMUFZJlNZ6LemDwFfjggAwAAACCAAMIBNRkKgJakKgJcxQVkmU1not6YPAV+OCADAAAAIIAAwgE1GQqAlqQqAlzFBWSZTWei3pg8BX44IAMAAAAggADCATUZCoCWpCoCXMUFZJlNZ6LemDwFfjggAwAAACCAAMIBNRkKgJakKgJcxQVkmU1not6YPAV+OCADAAAAIIAAwgE1GQqAlqQqAlzFBWSZTWei3pg8BX44IAMAAAAggADCATUZCoCWpCoCXMUFZJlNZ6LemDwFfjggAwAAACCAAMIBNRkKgJakKgJcxQVkmU1not6YPAV+OCADAAAAIIAAwgE1GQqAlqQqAlzFBWSZTWei3pg8BX44IAMAAAAggADCATUZCoCWpCoCXMUFZJlNZ6LemDwFfjggAwAAACCAAMIBNRkKgJakKgJcxQVkmU1kuvJCFAIpSiADgBAAIIABwM00E1SepopKSrpQIKdEKSTZKIArRSUlXCFJJ8xQVkmU1ntbvo0AV+OCACgAAAIIAAwgE1GQqAlqQqAlzFBWSZTWe1u+jQBX44IAKAAAAggADCATUZCoCWpCoCXMUFZJlNZ7W76NAFfjggAoAAACCAAMIBNRkKgJakKgJcxQVkmU1ntbvo0AV+OCACgAAAIIAAwgE1GQqAlqQqAlzFBWSZTWe1u+jQBX44IAKAAAAggADCATUZCoCWpCoCXMUFZJlNZ7W76NAFfjggAoAAACCAAMIBNRkKgJakKgJcxQVkmU1ntbvo0AV+OCACgAAAIIAAwgE1GQqAlqQqAlzFBWSZTWe1u+jQBX44IAKAAAAggADCATUZCoCWpCoCXMUFZJlNZ7W76NAFfjggAoAAACCAAMIBNRkKgJakKgJcxQVkmU1ntbvo0AV+OCACgAAAIIAAwgE1GQqAlqQqAlzFBWSZTWe1u+jQBX44IAKAAAAggADCATUZCoCWpCoCXMUFZJlNZ7W76NAFfjggAoAAACCAAMIBNRkKgJakKgJcxQVkmU1ntbvo0AV+OCACgAAAIIAAwgE1GQqAlqQqAlzFBWSZTWe1u+jQBX44IAKAAAAggADCATUZCoCWpCoCXMUFZJlNZ7W76NAFfjggAoAAACCAAMIBNRkKgJakKgJcxQVkmU1ntbvo0AV+OCACgAAAIIAAwgE1GQqAlqQqAlzFBWSZTWe1u+jQBX44IAKAAAAggADCATUZCoCWpCoCXMUFZJlNZ7W76NAFfjggAoAAACCAAMIBNRkKgJakKgJcxQVkmU1ntbvo0AV+OCACgAAAIIAAwgE1GQqAlqQqAlzFBWSZTWe1u+jQBX44IAKAAAAggADCATUZCoCWpCoCXMUFZJlNZ7W76NAFfjggAoAAACCAAMIBNRkKgJakKgJcxQVkmU1ntbvo0AV+OCACgAAAIIAAwgE1GQqAlqQqAlzFBWSZTWTNWeUMBFKWIALAEAAggAGoKUAUqPTiiRIYRVSqLAlSRtRUgViiRIehKkjzFBWSZTWeMFHnkBX44IAJAAAAggADCATUZCoCWpCoCXMUFZJlNZ4wUeeQFfjggAkAAACCAAMIBNRkKgJakKgJcxQVkmU1njBR55AV+OCACQAAAIIAAwgE1GQqAlqQqAlzFBWSZTWeMFHnkBX44IAJAAAAggADCATUZCoCWpCoCXMUFZJlNZ4wUeeQFfjggAkAAACCAAMIBNRkKgJakKgJcxQVkmU1njBR55AV+OCACQAAAIIAAwgE1GQqAlqQqAlzFBWSZTWeMFHnkBX44IAJAAAAggADCATUZCoCWpCoCXMUFZJlNZ4wUeeQFfjggAkAAACCAAMIBNRkKgJakKgJcxQVkmU1njBR55AV+OCACQAAAIIAAwgE1GQqAlqQqAlzFBWSZTWeMFHnkBX44IAJAAAAggADCATUZCoCWpCoCXMUFZJlNZ4wUeeQFfjggAkAAACCAAMIBNRkKgJakKgJcxQVkmU1njBR55AV+OCACQAAAIIAAwgE1GQqAlqQqAlzFBWSZTWeMFHnkBX44IAJAAAAggADCATUZCoCWpCoCXMUFZJlNZ4wUeeQFfjggAkAAACCAAMIBNRkKgJakKgJcxQVkmU1njBR55AV+OCACQAAAIIAAwgE1GQqAlqQqAlzFBWSZTWeMFHnkBX44IAJAAAAggADCATUZCoCWpCoCXMUFZJlNZ4wUeeQFfjggAkAAACCAAMIBNRkKgJakKgJcxQVkmU1njBR55AV+OCACQAAAIIAAwgE1GQqAlqQqAlzFBWSZTWeMFHnkBX44IAJAAAAggADCATUZCoCWpCoCXMUFZJlNZ4wUeeQFfjggAkAAACCAAMIBNRkKgJakKgJcxQVkmU1njBR55AV+OCACQAAAIIAAwgE1GQqAlqQqAlzFBWSZTWeMFHnkBX44IAJAAAAggADCATUZCoCWpCoCXMUFZJlNZ4wUeeQFfjggAkAAACCAAMIBNRkKgJakKgJcxQVkmU1mtxU0XAD9qCACYBAAIIABwM00ClJ6mklKq6qqFVOqEAjYUoClpJSquEQCPmKCskyms824hIQCvxwQARAAABBAAGEAmoyFQEtSFQEuYoKyTKazzbiEhAK/HBABEAAAEEAAYQCajIVAS1IVAS5igrJMprPNuISEAr8cEAEQAAAQQABhAJqMhUBLUhUBLmKCskyms824hIQCvxwQARAAABBAAGEAmoyFQEtSFQEuYoKyTKazzbiEhAK/HBABEAAAEEAAYQCajIVAS1IVAS5igrJMprPNuISEAr8cEAEQAAAQQABhAJqMhUBLUhUBLmKCskyms824hIQCvxwQARAAABBAAGEAmoyFQEtSFQEuYoKyTKazzbiEhAK/HBABEAAAEEAAYQCajIVAS1IVAS5igrJMprPNuISEAr8cEAEQAAAQQABhAJqMhUBLUhUBLmKCskyms824hIQCvxwQARAAABBAAGEAmoyFQEtSFQEuYoKyTKazzbiEhAK/HBABEAAAEEAAYQCajIVAS1IVAS5igrJMprPNuISEAr8cEAEQAAAQQABhAJqMhUBLUhUBLmKCskyms824hIQCvxwQARAAABBAAGEAmoyFQEtSFQEuYoKyTKazzbiEhAK/HBABEAAAEEAAYQCajIVAS1IVAS5igrJMprPNuISEAr8cEAEQAAAQQABhAJqMhUBLUhUBLmKCskyms824hIQCvxwQARAAABBAAGEAmoyFQEtSFQEuYoKyTKazzbiEhAK/HBABEAAAEEAAYQCajIVAS1IVAS5igrJMprPNuISEAr8cEAEQAAAQQABhAJqMhUBLUhUBLmKCskyms824hIQCvxwQARAAABBAAGEAmoyFQEtSFQEuYoKyTKazzbiEhAK/HBABEAAAEEAAYQCajIVAS1IVAS5igrJMprPNuISEAr8cEAEQAAAQQABhAJqMhUBLUhUBLmKCskyms824hIQCvxwQARAAABBAAGEAmoyFQEtSFQEuYoKyTKayOlbYVgGTehABGAgAEEAA4GaaCapPUxBFKcqFISuVSElbRQlVGIIpTpUhJXzFBWSZTWf/S1uMBX44IAIQAAAggADCATUZCoCWpCoCXMUFZJlNZ/9LW4wFfjggAhAAACCAAMIBNRkKgJakKgJcxQVkmU1n/0tbjAV+OCACEAAAIIAAwgE1GQqAlqQqAlzFBWSZTWf/S1uMBX44IAIQAAAggADCATUZCoCWpCoCXMUFZJlNZ/9LW4wFfjggAhAAACCAAMIBNRkKgJakKgJcxQVkmU1n/0tbjAV+OCACEAAAIIAAwgE1GQqAlqQqAlzFBWSZTWf/S1uMBX44IAIQAAAggADCATUZCoCWpCoCXMUFZJlNZ/9LW4wFfjggAhAAACCAAMIBNRkKgJakKgJcxQVkmU1n/0tbjAV+OCACEAAAIIAAwgE1GQqAlqQqAlzFBWSZTWf/S1uMBX44IAIQAAAggADCATUZCoCWpCoCXMUFZJlNZ/9LW4wFfjggAhAAACCAAMIBNRkKgJakKgJcxQVkmU1n/0tbjAV+OCACEAAAIIAAwgE1GQqAlqQqAlzFBWSZTWf/S1uMBX44IAIQAAAggADCATUZCoCWpCoCXMUFZJlNZ/9LW4wFfjggAhAAACCAAMIBNRkKgJakKgJcxQVkmU1n/0tbjAV+OCACEAAAIIAAwgE1GQqAlqQqAlzFBWSZTWf/S1uMBX44IAIQAAAggADCATUZCoCWpCoCXMUFZJlNZ/9LW4wFfjggAhAAACCAAMIBNRkKgJakKgJcxQVkmU1n/0tbjAV+OCACEAAAIIAAwgE1GQqAlqQqAlzFBWSZTWf/S1uMBX44IAIQAAAggADCATUZCoCWpCoCXMUFZJlNZ/9LW4wFfjggAhAAACCAAMIBNRkKgJakKgJcxQVkmU1n/0tbjAV+OCACEAAAIIAAwgE1GQqAlqQqAlzFBWSZTWf/S1uMBX44IAIQAAAggADCATUZCoCWpCoCXMUFZJlNZ9EMghAFUEAgAhgQACCAAUGaaBSk9TQQJJ1CgqqupVSmxKohoIEk4qqU+YoKyTKaz9BcVsAK/HBABBAAAEEAAYQCajIVAS1IVAS5igrJMprP0FxWwAr8cEAEEAAAQQABhAJqMhUBLUhUBLmKCskyms/QXFbACvxwQAQQAABBAAGEAmoyFQEtSFQEuYoKyTKaz9BcVsAK/HBABBAAAEEAAYQCajIVAS1IVAS5igrJMprP0FxWwAr8cEAEEAAAQQABhAJqMhUBLUhUBLmKCskyms/QXFbACvxwQAQQAABBAAGEAmoyFQEtSFQEuYoKyTKaz9BcVsAK/HBABBAAAEEAAYQCajIVAS1IVAS5igrJMprP0FxWwAr8cEAEEAAAQQABhAJqMhUBLUhUBLmKCskyms/QXFbACvxwQAQQAABBAAGEAmoyFQEtSFQEuYoKyTKaz9BcVsAK/HBABBAAAEEAAYQCajIVAS1IVAS5igrJMprP0FxWwAr8cEAEEAAAQQABhAJqMhUBLUhUBLmKCskyms/QXFbACvxwQAQQAABBAAGEAmoyFQEtSFQEuYoKyTKaz9BcVsAK/HBABBAAAEEAAYQCajIVAS1IVAS5igrJMprP0FxWwAr8cEAEEAAAQQABhAJqMhUBLUhUBLmKCskyms/QXFbACvxwQAQQAABBAAGEAmoyFQEtSFQEuYoKyTKaz9BcVsAK/HBABBAAAEEAAYQCajIVAS1IVAS5igrJMprP0FxWwAr8cEAEEAAAQQABhAJqMhUBLUhUBLmKCskyms/QXFbACvxwQAQQAABBAAGEAmoyFQEtSFQEuYoKyTKaz9BcVsAK/HBABBAAAEEAAYQCajIVAS1IVAS5igrJMprP0FxWwAr8cEAEEAAAQQABhAJqMhUBLUhUBLmKCskyms/QXFbACvxwQAQQAABBAAGEAmoyFQEtSFQEuYoKyTKaz9BcVsAK/HBABBAAAEEAAYQCajIVAS1IVAS5igrJMprP0FxWwAr8cEAEEAAAQQABhAJqMhUBLUhUBLmKCskymsiUnBUgA/akQAQYIABBAAOBmmgmqT1NJIgdAKgXShKqNlEqVJaSRA4oSqj5igrJMprPowN0qAr8cEAECAAAQQABhAJqMhUBLUhUBLmKCskyms+jA3SoCvxwQAQIAABBAAGEAmoyFQEtSFQEuYoKyTKaz6MDdKgK/HBABAgAAEEAAYQCajIVAS1IVAS5igrJMprPowN0qAr8cEAECAAAQQABhAJqMhUBLUhUBLmKCskyms+jA3SoCvxwQAQIAABBAAGEAmoyFQEtSFQEuYoKyTKaz6MDdKgK/HBABAgAAEEAAYQCajIVAS1IVAS5igrJMprPowN0qAr8cEAECAAAQQABhAJqMhUBLUhUBLmKCskyms+jA3SoCvxwQAQIAABBAAGEAmoyFQEtSFQEuYoKyTKaz6MDdKgK/HBABAgAAEEAAYQCajIVAS1IVAS5igrJMprPowN0qAr8cEAECAAAQQABhAJqMhUBLUhUBLmKCskyms+jA3SoCvxwQAQIAABBAAGEAmoyFQEtSFQEuYoKyTKaz6MDdKgK/HBABAgAAEEAAYQCajIVAS1IVAS5igrJMprPowN0qAr8cEAECAAAQQABhAJqMhUBLUhUBLmKCskyms+jA3SoCvxwQAQIAABBAAGEAmoyFQEtSFQEuYoKyTKaz6MDdKgK/HBABAgAAEEAAYQCajIVAS1IVAS5igrJMprPowN0qAr8cEAECAAAQQABhAJqMhUBLUhUBLmKCskyms+jA3SoCvxwQAQIAABBAAGEAmoyFQEtSFQEuYoKyTKaz6MDdKgK/HBABAgAAEEAAYQCajIVAS1IVAS5igrJMprPowN0qAr8cEAECAAAQQABhAJqMhUBLUhUBLmKCskyms+jA3SoCvxwQAQIAABBAAGEAmoyFQEtSFQEuYoKyTKaz6MDdKgK/HBABAgAAEEAAYQCajIVAS1IVAS5igrJMprPowN0qAr8cEAECAAAQQABhAJqMhUBLUhUBLmKCskyms4qxPEQCEk8QAQMIABBAAOBmmgUpPUwSIg4KpShcUUUm1RRQGCREHSiik+YoKyTKaz43JlXAK/HBABAQAAEEAAYQCajIVAS1IVAS5igrJMprPjcmVcAr8cEAEBAAAQQABhAJqMhUBLUhUBLmKCskyms+NyZVwCvxwQAQEAABBAAGEAmoyFQEtSFQEuYoKyTKaz43JlXAK/HBABAQAAEEAAYQCajIVAS1IVAS5igrJMprPjcmVcAr8cEAEBAAAQQABhAJqMhUBLUhUBLmKCskyms+NyZVwCvxwQAQEAABBAAGEAmoyFQEtSFQEuYoKyTKaz43JlXAK/HBABAQAAEEAAYQCajIVAS1IVAS5igrJMprPjcmVcAr8cEAEBAAAQQABhAJqMhUBLUhUBLmKCskyms+NyZVwCvxwQAQEAABBAAGEAmoyFQEtSFQEuYoKyTKaz43JlXAK/HBABAQAAEEAAYQCajIVAS1IVAS5igrJMprPjcmVcAr8cEAEBAAAQQABhAJqMhUBLUhUBLmKCskyms+NyZVwCvxwQAQEAABBAAGEAmoyFQEtSFQEuYoKyTKaz43JlXAK/HBABAQAAEEAAYQCajIVAS1IVAS5igrJMprPjcmVcAr8cEAEBAAAQQABhAJqMhUBLUhUBLmKCskyms+NyZVwCvxwQAQEAABBAAGEAmoyFQEtSFQEuYoKyTKaz43JlXAK/HBABAQAAEEAAYQCajIVAS1IVAS5igrJMprPjcmVcAr8cEAEBAAAQQABhAJqMhUBLUhUBLmKCskyms+NyZVwCvxwQAQEAABBAAGEAmoyFQEtSFQEuYoKyTKaz43JlXAK/HBABAQAAEEAAYQCajIVAS1IVAS5igrJMprPjcmVcAr8cEAEBAAAQQABhAJqMhUBLUhUBLmKCskyms+NyZVwCvxwQAQEAABBAAGEAmoyFQEtSFQEuYoKyTKaz43JlXAK/HBABAQAAEEAAYQCajIVAS1IVAS5igrJMprPjcmVcAr8cEAEBAAAQQABhAJqMhUBLUhUBLmKCskymswVrRDAAZ9gQAQEIABBAAGGYE1TTVECm1KIFPF3JFOFCQLW69vQ"))));
+?>
+--EXPECT--
+string(40) "d4b5e52ed34a774fa645f94369b0c61375436d30"