diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index 6c0489ff1dc..8161ea998c4 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -688,6 +688,21 @@ namespace ts {
             ch > CharacterCodes.maxAsciiCharacter && isUnicodeIdentifierPart(ch, languageVersion);
     }
 
+    /* @internal */
+    export function isIdentifier(name: string, languageVersion: ScriptTarget): boolean {
+        if (!isIdentifierStart(name.charCodeAt(0), languageVersion)) {
+            return false;
+        }
+
+        for (let i = 1, n = name.length; i < n; i++) {
+            if (!isIdentifierPart(name.charCodeAt(i), languageVersion)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     // Creates a scanner over a (possibly unspecified) range of a piece of text.
     export function createScanner(languageVersion: ScriptTarget,
                                   skipTrivia: boolean,
diff --git a/src/services/services.ts b/src/services/services.ts
index f2651163610..4efd87555a1 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -2978,15 +2978,9 @@ namespace ts {
             // e.g "b a" is valid quoted name but when we strip off the quotes, it is invalid.
             // We, thus, need to check if whatever was inside the quotes is actually a valid identifier name.
             if (performCharacterChecks) {
-                if (!isIdentifierStart(name.charCodeAt(0), target)) {
+                if (!isIdentifier(name, target)) {
                     return undefined;
                 }
-
-                for (let i = 1, n = name.length; i < n; i++) {
-                    if (!isIdentifierPart(name.charCodeAt(i), target)) {
-                        return undefined;
-                    }
-                }
             }
 
             return name;