diff --git a/src/api.cc b/src/api.cc
index 2b24ab07f6..9ee23698cf 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -4061,7 +4061,7 @@ bool String::IsOneByte() const {
   if (IsDeadCheck(str->GetIsolate(), "v8::String::IsOneByte()")) {
     return false;
   }
-  return str->IsOneByteConvertible();
+  return str->HasOnlyOneByteChars();
 }
 
 
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 08378f1955..804cd26dab 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -357,12 +357,8 @@ bool String::IsTwoByteRepresentationUnderneath() {
 
 bool String::HasOnlyOneByteChars() {
   uint32_t type = map()->instance_type();
-  return (type & kOneByteDataHintMask) == kOneByteDataHintTag;
-}
-
-
-bool String::IsOneByteConvertible() {
-  return HasOnlyOneByteChars() || IsOneByteRepresentation();
+  return (type & kOneByteDataHintMask) == kOneByteDataHintTag ||
+         IsOneByteRepresentation();
 }
 
 
diff --git a/src/objects.h b/src/objects.h
index e32c41bb13..941ee26c4b 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -7638,8 +7638,6 @@ class String: public Name {
   // possible.
   inline bool HasOnlyOneByteChars();
 
-  inline bool IsOneByteConvertible();
-
   // Get and set individual two byte chars in the string.
   inline void Set(int index, uint16_t value);
   // Get individual two byte char in the string.  Repeated calls
diff --git a/src/runtime.cc b/src/runtime.cc
index 333d22a344..5c1cde2bf5 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -3347,8 +3347,8 @@ MUST_USE_RESULT static MaybeObject* StringReplaceGlobalRegExpWithString(
 
   // Shortcut for simple non-regexp global replacements
   if (regexp->TypeTag() == JSRegExp::ATOM && simple_replace) {
-    if (subject->IsOneByteConvertible() &&
-        replacement->IsOneByteConvertible()) {
+    if (subject->HasOnlyOneByteChars() &&
+        replacement->HasOnlyOneByteChars()) {
       return StringReplaceGlobalAtomRegExpWithString<SeqOneByteString>(
           isolate, subject, regexp, replacement, last_match_info);
     } else {
@@ -3530,7 +3530,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_StringReplaceGlobalRegExpWithString) {
   if (!subject->IsFlat()) subject = FlattenGetString(subject);
 
   if (replacement->length() == 0) {
-    if (subject->IsOneByteConvertible()) {
+    if (subject->HasOnlyOneByteChars()) {
       return StringReplaceGlobalRegExpWithEmptyString<SeqOneByteString>(
           isolate, subject, regexp, last_match_info);
     } else {
@@ -6389,7 +6389,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_StringBuilderConcat) {
     if (first->IsString()) return first;
   }
 
-  bool one_byte = special->IsOneByteConvertible();
+  bool one_byte = special->HasOnlyOneByteChars();
   int position = 0;
   for (int i = 0; i < array_length; i++) {
     int increment = 0;
@@ -6430,7 +6430,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_StringBuilderConcat) {
       String* element = String::cast(elt);
       int element_length = element->length();
       increment = element_length;
-      if (one_byte && !element->IsOneByteConvertible()) {
+      if (one_byte && !element->HasOnlyOneByteChars()) {
         one_byte = false;
       }
     } else {