diff --git a/implementation-contributed/v8/mjsunit/harmony/to-number.js b/implementation-contributed/v8/mjsunit/harmony/to-number.js
index c5a06cf4ffe..e145782d4b9 100644
--- a/implementation-contributed/v8/mjsunit/harmony/to-number.js
+++ b/implementation-contributed/v8/mjsunit/harmony/to-number.js
@@ -20,6 +20,7 @@ assertEquals(-1, %ToNumber("-1"));
 assertEquals(123, %ToNumber("123"));
 assertEquals(NaN, %ToNumber("random text"));
 assertEquals(NaN, %ToNumber("INFINITY"));
+assertEquals(NaN, %ToNumber("infinity"));
 
 assertThrows(function() { %ToNumber(Symbol.toPrimitive) }, TypeError);
 
diff --git a/test/built-ins/Number/S15.7.1.1_A1.js b/test/built-ins/Number/S15.7.1.1_A1.js
index ebecc20106c..adf4f19515e 100644
--- a/test/built-ins/Number/S15.7.1.1_A1.js
+++ b/test/built-ins/Number/S15.7.1.1_A1.js
@@ -25,3 +25,4 @@ assert.sameValue(
 
 assert.sameValue(Number("abc"), NaN, 'Number("abc") returns NaN');
 assert.sameValue(Number("INFINITY"), NaN, 'Number("INFINITY") returns NaN');
+assert.sameValue(Number("infinity"), NaN, 'Number("infinity") returns NaN');
diff --git a/test/language/expressions/unary-plus/S11.4.6_A3_T3.js b/test/language/expressions/unary-plus/S11.4.6_A3_T3.js
index cb6c4546156..9a3a2f6b49f 100644
--- a/test/language/expressions/unary-plus/S11.4.6_A3_T3.js
+++ b/test/language/expressions/unary-plus/S11.4.6_A3_T3.js
@@ -26,3 +26,8 @@ if (isNaN(+"x") !== true) {
 if (isNaN(+"INFINITY") !== true) {
   throw new Test262Error('#4: +"INFINITY" === Not-a-Number. Actual: ' + (+"INFINITY"));
 }
+
+//CHECK#5
+if (isNaN(+"infinity") !== true) {
+  throw new Test262Error('#5: +"infinity" === Not-a-Number. Actual: ' + (+"infinity"));
+}