diff --git a/scripts/configureNightly.ts b/scripts/configureNightly.ts
index 640f330b376..778f5ce3727 100644
--- a/scripts/configureNightly.ts
+++ b/scripts/configureNightly.ts
@@ -19,47 +19,57 @@ function main(): void {
 
     // Acquire the version from the package.json file and modify it appropriately.
     const packageJsonFilePath = ts.normalizePath(sys.args[0]);
-    const packageJsonContents = sys.readFile(packageJsonFilePath);
-    const packageJsonValue: PackageJson = JSON.parse(packageJsonContents);
+    const packageJsonValue: PackageJson = JSON.parse(sys.readFile(packageJsonFilePath));
 
-    const nightlyVersion = getNightlyVersionString(packageJsonValue.version);
-
-    // Modify the package.json structure
-    packageJsonValue.version = nightlyVersion;
+    const { majorMinor, patch } = parsePackageJsonVersion(packageJsonValue.version);
+    const nightlyPatch = getNightlyPatch(patch);
 
     // Acquire and modify the source file that exposes the version string.
     const tsFilePath = ts.normalizePath(sys.args[1]);
-    const tsFileContents = sys.readFile(tsFilePath);
-    const versionAssignmentRegExp = /export\s+const\s+version\s+=\s+".*";/;
-    const modifiedTsFileContents = tsFileContents.replace(versionAssignmentRegExp, `export const version = "${nightlyVersion}";`);
+    const tsFileContents = ts.sys.readFile(tsFilePath);
+    const modifiedTsFileContents = updateTsFile(tsFilePath, tsFileContents, majorMinor, patch, nightlyPatch);
 
     // Ensure we are actually changing something - the user probably wants to know that the update failed.
     if (tsFileContents === modifiedTsFileContents) {
         let err = `\n  '${tsFilePath}' was not updated while configuring for a nightly publish.\n    `;
-
-        if (tsFileContents.match(versionAssignmentRegExp)) {
-            err += `Ensure that you have not already run this script; otherwise, erase your changes using 'git checkout -- "${tsFilePath}"'.`;
-        }
-        else {
-            err += `The file seems to no longer have a string matching '${versionAssignmentRegExp}'.`;
-        }
-
+        err += `Ensure that you have not already run this script; otherwise, erase your changes using 'git checkout -- "${tsFilePath}"'.`;
         throw err + "\n";
     }
 
     // Finally write the changes to disk.
+    // Modify the package.json structure
+    packageJsonValue.version = `${majorMinor}.${nightlyPatch}`;
     sys.writeFile(packageJsonFilePath, JSON.stringify(packageJsonValue, /*replacer:*/ undefined, /*space:*/ 4))
     sys.writeFile(tsFilePath, modifiedTsFileContents);
 }
 
-function getNightlyVersionString(versionString: string): string {
-    // If the version string already contains "-nightly",
-    // then get the base string and update based on that.
-    const dashNightlyPos = versionString.indexOf("-dev");
-    if (dashNightlyPos >= 0) {
-        versionString = versionString.slice(0, dashNightlyPos);
+function updateTsFile(tsFilePath: string, tsFileContents: string, majorMinor: string, patch: string, nightlyPatch: string): string {
+    const majorMinorRgx = /export const versionMajorMinor = "(\d+\.\d+)"/;
+    const majorMinorMatch = majorMinorRgx.exec(tsFileContents);
+    ts.Debug.assert(majorMinorMatch !== null, "", () => `The file seems to no longer have a string matching '${majorMinorRgx}'.`);
+    const parsedMajorMinor = majorMinorMatch[1];
+    ts.Debug.assert(parsedMajorMinor === majorMinor, "versionMajorMinor does not match.", () => `${tsFilePath}: '${parsedMajorMinor}'; package.json: '${majorMinor}'`);
+
+    const versionRgx = /export const version = `\$\{versionMajorMinor\}\.(\d)`;/;
+    const patchMatch = versionRgx.exec(tsFileContents);
+    ts.Debug.assert(patchMatch !== null, "The file seems to no longer have a string matching", () => versionRgx.toString());
+    const parsedPatch = patchMatch[1];
+    if (parsedPatch !== patch) {
+        throw new Error(`patch does not match. ${tsFilePath}: '${parsedPatch}; package.json: '${patch}'`);
     }
 
+    return tsFileContents.replace(versionRgx, `export const version = \`\${versionMajorMinor}.${nightlyPatch}\`;`);
+}
+
+function parsePackageJsonVersion(versionString: string): { majorMinor: string, patch: string } {
+    const versionRgx = /(\d+\.\d+)\.(\d+)($|\-)/;
+    const match = versionString.match(versionRgx);
+    ts.Debug.assert(match !== null, "package.json 'version' should match", () => versionRgx.toString());
+    return { majorMinor: match[1], patch: match[2] };
+}
+
+/** e.g. 0-dev.20170707 */
+function getNightlyPatch(plainPatch: string): string {
     // We're going to append a representation of the current time at the end of the current version.
     // String.prototype.toISOString() returns a 24-character string formatted as 'YYYY-MM-DDTHH:mm:ss.sssZ',
     // but we'd prefer to just remove separators and limit ourselves to YYYYMMDD.
@@ -67,7 +77,7 @@ function getNightlyVersionString(versionString: string): string {
     const now = new Date();
     const timeStr = now.toISOString().replace(/:|T|\.|-/g, "").slice(0, 8);
 
-    return `${versionString}-dev.${timeStr}`;
+    return `${plainPatch}-dev.${timeStr}`;
 }
 
 main();
\ No newline at end of file
diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index cecf88f42ce..a72a257a400 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -2,6 +2,8 @@
 /// <reference path="performance.ts" />
 
 namespace ts {
+    // WARNING: The script `configureNightly.ts` uses a regexp to parse out these values.
+    // If changing the text in this section, be sure to test `configureNightly` too.
     export const versionMajorMinor = "2.5";
     /** The version of the TypeScript compiler release */
     export const version = `${versionMajorMinor}.0`;