diff --git a/libraries/stdlib/js-ir/runtime/longjs.kt b/libraries/stdlib/js-ir/runtime/longjs.kt
index 77121b40e25..7758c3e9246 100644
--- a/libraries/stdlib/js-ir/runtime/longjs.kt
+++ b/libraries/stdlib/js-ir/runtime/longjs.kt
@@ -335,13 +335,13 @@ internal fun Long.shiftRightUnsigned(numBits: Int): Long {
 internal fun fromInt(value: Int) = Long(value, if (value < 0) -1 else 0)
 
 /**
- * Returns a Long representing the given value, provided that it is a finite
- * number.  Otherwise, zero is returned.
- * @param {number} value The number in question.
- * @return {!Kotlin.Long} The corresponding Long value.
+ * Converts this [Double] value to [Long].
+ * The fractional part, if any, is rounded down.
+ * Returns zero if this `Double` value is `NaN`, [Long.MIN_VALUE] if it's less than `Long.MIN_VALUE`,
+ * [Long.MAX_VALUE] if it's bigger than `Long.MAX_VALUE`.
  */
 internal fun fromNumber(value: Double): Long {
-    if (value.isNaN() || !value.isFinite()) {
+    if (value.isNaN()) {
         return ZERO;
     } else if (value <= -TWO_PWR_63_DBL_) {
         return MIN_VALUE;
diff --git a/libraries/stdlib/js-v1/src/js/long.js b/libraries/stdlib/js-v1/src/js/long.js
index e8e7b70a874..369679c22b3 100644
--- a/libraries/stdlib/js-v1/src/js/long.js
+++ b/libraries/stdlib/js-v1/src/js/long.js
@@ -94,13 +94,15 @@ Kotlin.Long.fromInt = function(value) {
 
 
 /**
- * Returns a Long representing the given value, provided that it is a finite
- * number.  Otherwise, zero is returned.
+ * Converts this number value to `Long`.
+ * The fractional part, if any, is rounded down.
+ * Returns zero if this `Double` value is `NaN`, `Long.MIN_VALUE` if it's less than `Long.MIN_VALUE`,
+ * `Long.MAX_VALUE` if it's bigger than `Long.MAX_VALUE`.
  * @param {number} value The number in question.
  * @return {!Kotlin.Long} The corresponding Long value.
  */
 Kotlin.Long.fromNumber = function(value) {
-  if (isNaN(value) || !isFinite(value)) {
+  if (isNaN(value)) {
     return Kotlin.Long.ZERO;
   } else if (value <= -Kotlin.Long.TWO_PWR_63_DBL_) {
     return Kotlin.Long.MIN_VALUE;