diff --git a/backend.native/tests/build.gradle b/backend.native/tests/build.gradle
index 27e4e7d604b..7f33d7778f2 100644
--- a/backend.native/tests/build.gradle
+++ b/backend.native/tests/build.gradle
@@ -879,7 +879,7 @@ task string_builder0(type: RunKonanTest) {
 }
 
 task string0(type: RunKonanTest) {
-    goldValue = "true\ntrue\nПРИВЕТ\nпривет\nПока\n"
+    goldValue = "true\ntrue\nПРИВЕТ\nпривет\nПока\ntrue\n"
     source = "runtime/text/string0.kt"
 }
 
diff --git a/backend.native/tests/runtime/text/string0.kt b/backend.native/tests/runtime/text/string0.kt
index 069c3d47f9e..eb0a4b42dbf 100644
--- a/backend.native/tests/runtime/text/string0.kt
+++ b/backend.native/tests/runtime/text/string0.kt
@@ -6,4 +6,5 @@ fun main(args: Array<String>) {
     println(strI18n.toUpperCase())
     println(strI18n.toLowerCase())
     println("пока".capitalize())
+    println("http://jetbrains.com".startsWith("http://"))
 }
\ No newline at end of file
diff --git a/runtime/src/main/kotlin/konan/internal/Strings.kt b/runtime/src/main/kotlin/konan/internal/Strings.kt
index 240d9cae55e..1f4d63d8819 100644
--- a/runtime/src/main/kotlin/konan/internal/Strings.kt
+++ b/runtime/src/main/kotlin/konan/internal/Strings.kt
@@ -75,28 +75,6 @@ public fun String.replaceFirst(oldValue: String, newValue: String, ignoreCase: B
     return if (index < 0) this else this.replaceRange(index, index + oldValue.length, newValue)
 }
 
-/**
- * Returns a copy of this string converted to upper case using the rules of the default locale.
- */
-@SymbolName("Kotlin_String_toUpperCase")
-external public fun String.toUpperCase(): String
-
-/**
- * Returns a copy of this string converted to lower case using the rules of the default locale.
- */
-@SymbolName("Kotlin_String_toLowerCase")
-external public inline fun String.toLowerCase(): String
-
-/**
- * Returns a copy of this string having its first letter uppercased, or the original string,
- * if it's empty or already starts with an upper case letter.
- *
- * @sample samples.text.Strings.captialize
- */
-public fun String.capitalize(): String {
-    return if (isNotEmpty() && this[0].isLowerCase()) substring(0, 1).toUpperCase() + substring(1) else this
-}
-
 /**
  * Returns a copy of this string having its first letter lowercased, or the original string,
  * if it's empty or already starts with a lower case letter.
@@ -112,6 +90,34 @@ public fun String.decapitalize(): String {
  */
 public fun CharSequence.isBlank(): Boolean = length == 0 || indices.all { this[it].isWhitespace() }
 
+/**
+ * Returns the substring of this string starting at the [startIndex] and ending right before the [endIndex].
+ *
+ * @param startIndex the start index (inclusive).
+ * @param endIndex the end index (exclusive).
+ */
+@kotlin.internal.InlineOnly
+public inline fun String.substring(startIndex: Int, endIndex: Int): String =
+        subSequence(startIndex, endIndex) as String
+
+/**
+ * Returns `true` if this string starts with the specified prefix.
+ */
+public fun String.startsWith(prefix: String, ignoreCase: Boolean = false): Boolean =
+        regionMatches(0, prefix, 0, prefix.length, ignoreCase)
+
+/**
+ * Returns `true` if a substring of this string starting at the specified offset [startIndex] starts with the specified prefix.
+ */
+public fun String.startsWith(prefix: String, startIndex: Int, ignoreCase: Boolean = false): Boolean =
+        regionMatches(startIndex, prefix, 0, prefix.length, ignoreCase)
+
+/**
+ * Returns `true` if this string ends with the specified suffix.
+ */
+public fun String.endsWith(suffix: String, ignoreCase: Boolean = false): Boolean =
+        regionMatches(length - suffix.length, suffix, 0, suffix.length, ignoreCase)
+
 /**
  * Returns `true` if the specified range in this char sequence is equal to the specified range in another char sequence.
  * @param thisOffset the start offset in this char sequence of the substring to compare.
@@ -136,3 +142,25 @@ external public fun CharSequence.regionMatches(
 external public fun String.regionMatches(
         thisOffset: Int, other: String, otherOffset: Int, length: Int,
         ignoreCase: Boolean = false): Boolean
+
+/**
+ * Returns a copy of this string converted to upper case using the rules of the default locale.
+ */
+@SymbolName("Kotlin_String_toUpperCase")
+external public fun String.toUpperCase(): String
+
+/**
+ * Returns a copy of this string converted to lower case using the rules of the default locale.
+ */
+@SymbolName("Kotlin_String_toLowerCase")
+external public inline fun String.toLowerCase(): String
+
+/**
+ * Returns a copy of this string having its first letter uppercased, or the original string,
+ * if it's empty or already starts with an upper case letter.
+ *
+ * @sample samples.text.Strings.captialize
+ */
+public fun String.capitalize(): String {
+    return if (isNotEmpty() && this[0].isLowerCase()) substring(0, 1).toUpperCase() + substring(1) else this
+}
\ No newline at end of file
diff --git a/runtime/src/main/kotlin/kotlin/text/Strings.kt b/runtime/src/main/kotlin/kotlin/text/Strings.kt
index 0d1e5db58f9..b913143f903 100644
--- a/runtime/src/main/kotlin/kotlin/text/Strings.kt
+++ b/runtime/src/main/kotlin/kotlin/text/Strings.kt
@@ -712,7 +712,7 @@ public fun CharSequence.endsWith(char: Char, ignoreCase: Boolean = false): Boole
  */
 public fun CharSequence.startsWith(prefix: CharSequence, ignoreCase: Boolean = false): Boolean {
     if (!ignoreCase && this is String && prefix is String)
-        return this.startsWith(prefix)
+        return (this as String).startsWith(prefix)
     else
         return regionMatchesImpl(0, prefix, 0, prefix.length, ignoreCase)
 }
@@ -722,7 +722,7 @@ public fun CharSequence.startsWith(prefix: CharSequence, ignoreCase: Boolean = f
  */
 public fun CharSequence.startsWith(prefix: CharSequence, startIndex: Int, ignoreCase: Boolean = false): Boolean {
     if (!ignoreCase && this is String && prefix is String)
-        return this.startsWith(prefix, startIndex)
+        return (this as String).startsWith(prefix, startIndex)
     else
         return regionMatchesImpl(startIndex, prefix, 0, prefix.length, ignoreCase)
 }
@@ -732,7 +732,7 @@ public fun CharSequence.startsWith(prefix: CharSequence, startIndex: Int, ignore
  */
 public fun CharSequence.endsWith(suffix: CharSequence, ignoreCase: Boolean = false): Boolean {
     if (!ignoreCase && this is String && suffix is String)
-        return this.endsWith(suffix)
+        return (this as String).endsWith(suffix)
     else
         return regionMatchesImpl(length - suffix.length, suffix, 0, suffix.length, ignoreCase)
 }