diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
index f6024ed258d..7fb308912c3 100644
--- a/src/compiler/moduleNameResolver.ts
+++ b/src/compiler/moduleNameResolver.ts
@@ -769,7 +769,7 @@ namespace ts {
             const loader: ResolutionKindSpecificLoader = (extensions, candidate, failedLookupLocations, onlyRecordFailures, state) => nodeLoadModuleByRelativeName(extensions, candidate, failedLookupLocations, onlyRecordFailures, state, /*considerPackageJson*/ true);
             const resolved = tryLoadModuleUsingOptionalResolutionSettings(extensions, moduleName, containingDirectory, loader, failedLookupLocations, state);
             if (resolved) {
-                return toSearchResult({ resolved, isExternalLibraryImport: resolved.path.indexOf("/node_modules/") !== -1 });
+                return toSearchResult({ resolved, isExternalLibraryImport: stringContains(resolved.path, nodeModulesPathPart) });
             }
 
             if (!isExternalModuleNameRelative(moduleName)) {
@@ -843,7 +843,8 @@ namespace ts {
         return loadNodeModuleFromDirectory(extensions, candidate, failedLookupLocations, onlyRecordFailures, state, considerPackageJson);
     }
 
-    const nodeModulesPathPart = "/node_modules/";
+    /*@internal*/
+    export const nodeModulesPathPart = "/node_modules/";
 
     /**
      * This will be called on the successfully resolved path from `loadModuleFromFile`.
diff --git a/src/compiler/moduleSpecifiers.ts b/src/compiler/moduleSpecifiers.ts
index e56951cb507..8c695e10be2 100644
--- a/src/compiler/moduleSpecifiers.ts
+++ b/src/compiler/moduleSpecifiers.ts
@@ -401,7 +401,7 @@ namespace ts.moduleSpecifiers {
             partEnd = fullPath.indexOf("/", partStart + 1);
             switch (state) {
                 case States.BeforeNodeModules:
-                    if (fullPath.indexOf("/node_modules/", partStart) === partStart) {
+                    if (fullPath.indexOf(nodeModulesPathPart, partStart) === partStart) {
                         topLevelNodeModulesIndex = partStart;
                         topLevelPackageNameIndex = partEnd;
                         state = States.NodeModules;
@@ -418,7 +418,7 @@ namespace ts.moduleSpecifiers {
                     }
                     break;
                 case States.PackageContent:
-                    if (fullPath.indexOf("/node_modules/", partStart) === partStart) {
+                    if (fullPath.indexOf(nodeModulesPathPart, partStart) === partStart) {
                         state = States.NodeModules;
                     }
                     else {
diff --git a/src/compiler/resolutionCache.ts b/src/compiler/resolutionCache.ts
index ae451ae302d..2d7bcb34c2d 100644
--- a/src/compiler/resolutionCache.ts
+++ b/src/compiler/resolutionCache.ts
@@ -419,7 +419,7 @@ namespace ts {
 
         function getDirectoryToWatchFromFailedLookupLocationDirectory(dir: string, dirPath: Path) {
             // If directory path contains node module, get the most parent node_modules directory for watching
-            while (stringContains(dirPath, "/node_modules/")) {
+            while (stringContains(dirPath, nodeModulesPathPart)) {
                 dir = getDirectoryPath(dir);
                 dirPath = getDirectoryPath(dirPath);
             }