diff --git a/src/15utility.js b/src/15utility.js
index 5f2c40559b..b89d6451f9 100755
--- a/src/15utility.js
+++ b/src/15utility.js
@@ -934,6 +934,18 @@ var arrayIntersectDeep = (utils.arrayIntersectDeep = function (a, b) {
 	return r;
 });
 
+/**
+  SUBSTRING with MySQL semantics for a non-positive start: a start of 0 returns
+  '', a negative start counts from the end of the string, and a start that
+  reaches before the string start returns ''. `len` is optional.
+  */
+var substr = (utils.substr = function substr(str, start, len) {
+	if (start == 0) return '';
+	var from = start < 0 ? str.length + start : start - 1;
+	if (from < 0) return '';
+	return len === undefined ? str.substr(from) : str.substr(from, len);
+});
+
 /**
   Deep clone objects
   */
diff --git a/src/55functions.js b/src/55functions.js
index 9bdc42ff24..627d0cc773 100644
--- a/src/55functions.js
+++ b/src/55functions.js
@@ -186,8 +186,8 @@ stdlib.SUBSTRING =
 	stdlib.SUBSTR =
 	stdlib.MID =
 		function (a, b, c) {
-			if (arguments.length == 2) return und(a, 'y.substr(' + b + '-1)');
-			else if (arguments.length == 3) return und(a, 'y.substr(' + b + '-1,' + c + ')');
+			if (arguments.length == 2) return und(a, 'alasql.utils.substr(y,' + b + ')');
+			else if (arguments.length == 3) return und(a, 'alasql.utils.substr(y,' + b + ',' + c + ')');
 		};
 
 stdfn.REGEXP_LIKE = function (a, b, c) {
diff --git a/test/test-substring-negative-start.js b/test/test-substring-negative-start.js
new file mode 100644
index 0000000000..a07e86b525
--- /dev/null
+++ b/test/test-substring-negative-start.js
@@ -0,0 +1,35 @@
+if (typeof exports === 'object') {
+	var assert = require('assert');
+	var alasql = require('..');
+}
+
+describe('SUBSTRING with non-positive start position', function () {
+	it('follows MySQL semantics for start = 0', function () {
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', 0, 3)"), '');
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', 0)"), '');
+	});
+
+	it('follows MySQL semantics for a negative start (counts from the end)', function () {
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', -1, 3)"), 'f');
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', -2, 3)"), 'ef');
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', -2)"), 'ef');
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', -6)"), 'abcdef');
+	});
+
+	it('returns empty when a negative start reaches past the string start', function () {
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', -7, 3)"), '');
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', -10, 3)"), '');
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', -7)"), '');
+	});
+
+	it('leaves positive start positions unchanged', function () {
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', 1, 3)"), 'abc');
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', 2, 3)"), 'bcd');
+		assert.strictEqual(alasql("SELECT VALUE SUBSTRING('abcdef', 4)"), 'def');
+	});
+
+	it('applies the same rules to the SUBSTR and MID aliases', function () {
+		assert.strictEqual(alasql("SELECT VALUE SUBSTR('abcdef', 0, 3)"), '');
+		assert.strictEqual(alasql("SELECT VALUE MID('abcdef', -2, 3)"), 'ef');
+	});
+});