diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
index d67bf107a8..7fb308912c 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: false });
+                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 e56951cb50..8c695e10be 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 ae451ae302..2d7bcb34c2 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);
             }
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.js b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.js
new file mode 100644
index 0000000000..b7f90ca24d
--- /dev/null
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.js
@@ -0,0 +1,12 @@
+//// [tests/cases/compiler/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.ts] ////
+
+//// [foobar.js]
+module.exports = { a: 10 };
+
+//// [a.ts]
+import foobar from "foo/bar/foobar.js";
+
+
+//// [/bin/a.js]
+"use strict";
+exports.__esModule = true;
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.symbols b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.symbols
new file mode 100644
index 0000000000..f6041ba8e3
--- /dev/null
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.symbols
@@ -0,0 +1,4 @@
+=== /a.ts ===
+import foobar from "foo/bar/foobar.js";
+>foobar : Symbol(foobar, Decl(a.ts, 0, 6))
+
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.trace.json
new file mode 100644
index 0000000000..dac9d19bc0
--- /dev/null
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.trace.json
@@ -0,0 +1,10 @@
+[
+    "======== Resolving module 'foo/bar/foobar.js' from '/a.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "'baseUrl' option is set to '/', using this value to resolve non-relative module name 'foo/bar/foobar.js'.",
+    "'paths' option is specified, looking for a pattern to match module name 'foo/bar/foobar.js'.",
+    "Module name 'foo/bar/foobar.js', matched pattern '*'.",
+    "Trying substitution 'node_modules/*', candidate module location: 'node_modules/foo/bar/foobar.js'.",
+    "File '/node_modules/foo/bar/foobar.js' exist - use it as a name resolution result.",
+    "======== Module name 'foo/bar/foobar.js' was successfully resolved to '/node_modules/foo/bar/foobar.js'. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.types b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.types
new file mode 100644
index 0000000000..829c950773
--- /dev/null
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.types
@@ -0,0 +1,4 @@
+=== /a.ts ===
+import foobar from "foo/bar/foobar.js";
+>foobar : any
+
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.ts b/tests/cases/compiler/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.ts
new file mode 100644
index 0000000000..99e4070ff8
--- /dev/null
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution_withExtension_MapedToNodeModules.ts
@@ -0,0 +1,23 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @allowJs: true
+// @esModuleInterop: true
+// @fullEmitPaths: true
+
+// @Filename: /node_modules/foo/bar/foobar.js
+module.exports = { a: 10 };
+
+// @Filename: /a.ts
+import foobar from "foo/bar/foobar.js";
+
+// @Filename: /tsconfig.json
+{
+    "compilerOptions": {
+        "baseUrl": ".",
+        "paths": {
+            "*": ["node_modules/*", "src/types"]
+        },
+        "allowJs": true,
+        "outDir": "bin"
+    }
+}