diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
index e4edfe68df..4c6616c36d 100644
--- a/src/compiler/moduleNameResolver.ts
+++ b/src/compiler/moduleNameResolver.ts
@@ -653,11 +653,13 @@ namespace ts {
                 if (state.traceEnabled) {
                     trace(state.host, Diagnostics.Trying_substitution_0_candidate_module_location_Colon_1, subst, path);
                 }
-                // A path mapping may have a ".ts" extension; in contrast to an import, which should omit it.
-                const tsExtension = tryGetExtensionFromPath(candidate);
-                if (tsExtension !== undefined) {
+                // A path mapping may have an extension, in contrast to an import, which should omit it.
+                const extension = tryGetExtensionFromPath(candidate);
+                if (extension !== undefined) {
                     const path = tryFile(candidate, failedLookupLocations, /*onlyRecordFailures*/ false, state);
-                    return path && { path, extension: tsExtension };
+                    if (path !== undefined) {
+                        return { path, extension };
+                    }
                 }
 
                 return loader(extensions, candidate, failedLookupLocations, !directoryProbablyExists(getDirectoryPath(candidate), state.host), state);
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.js b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.js
new file mode 100644
index 0000000000..c54c0ba61e
--- /dev/null
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.js
@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/pathMappingBasedModuleResolution_withExtensionInName.ts] ////
+
+//// [index.d.ts]
+export const x: number;
+
+//// [index.d.ts]
+export const y: number;
+
+//// [a.ts]
+import { x } from "zone.js";
+import { y } from "zone.tsx";
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.symbols b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.symbols
new file mode 100644
index 0000000000..440ef2d294
--- /dev/null
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.symbols
@@ -0,0 +1,15 @@
+=== /a.ts ===
+import { x } from "zone.js";
+>x : Symbol(x, Decl(a.ts, 0, 8))
+
+import { y } from "zone.tsx";
+>y : Symbol(y, Decl(a.ts, 1, 8))
+
+=== /foo/zone.js/index.d.ts ===
+export const x: number;
+>x : Symbol(x, Decl(index.d.ts, 0, 12))
+
+=== /foo/zone.tsx/index.d.ts ===
+export const y: number;
+>y : Symbol(y, Decl(index.d.ts, 0, 12))
+
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.trace.json
new file mode 100644
index 0000000000..216442fb37
--- /dev/null
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.trace.json
@@ -0,0 +1,38 @@
+[
+    "======== Resolving module 'zone.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 'zone.js'.",
+    "'paths' option is specified, looking for a pattern to match module name 'zone.js'.",
+    "Module name 'zone.js', matched pattern '*'.",
+    "Trying substitution 'foo/*', candidate module location: 'foo/zone.js'.",
+    "File '/foo/zone.js' does not exist.",
+    "Loading module as file / folder, candidate module location '/foo/zone.js', target file type 'TypeScript'.",
+    "File '/foo/zone.js.ts' does not exist.",
+    "File '/foo/zone.js.tsx' does not exist.",
+    "File '/foo/zone.js.d.ts' does not exist.",
+    "File name '/foo/zone.js' has a '.js' extension - stripping it.",
+    "File '/foo/zone.ts' does not exist.",
+    "File '/foo/zone.tsx' does not exist.",
+    "File '/foo/zone.d.ts' does not exist.",
+    "File '/foo/zone.js/package.json' does not exist.",
+    "File '/foo/zone.js/index.ts' does not exist.",
+    "File '/foo/zone.js/index.tsx' does not exist.",
+    "File '/foo/zone.js/index.d.ts' exist - use it as a name resolution result.",
+    "======== Module name 'zone.js' was successfully resolved to '/foo/zone.js/index.d.ts'. ========",
+    "======== Resolving module 'zone.tsx' 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 'zone.tsx'.",
+    "'paths' option is specified, looking for a pattern to match module name 'zone.tsx'.",
+    "Module name 'zone.tsx', matched pattern '*'.",
+    "Trying substitution 'foo/*', candidate module location: 'foo/zone.tsx'.",
+    "File '/foo/zone.tsx' does not exist.",
+    "Loading module as file / folder, candidate module location '/foo/zone.tsx', target file type 'TypeScript'.",
+    "File '/foo/zone.tsx.ts' does not exist.",
+    "File '/foo/zone.tsx.tsx' does not exist.",
+    "File '/foo/zone.tsx.d.ts' does not exist.",
+    "File '/foo/zone.tsx/package.json' does not exist.",
+    "File '/foo/zone.tsx/index.ts' does not exist.",
+    "File '/foo/zone.tsx/index.tsx' does not exist.",
+    "File '/foo/zone.tsx/index.d.ts' exist - use it as a name resolution result.",
+    "======== Module name 'zone.tsx' was successfully resolved to '/foo/zone.tsx/index.d.ts'. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.types b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.types
new file mode 100644
index 0000000000..7fd8a2710c
--- /dev/null
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtensionInName.types
@@ -0,0 +1,15 @@
+=== /a.ts ===
+import { x } from "zone.js";
+>x : number
+
+import { y } from "zone.tsx";
+>y : number
+
+=== /foo/zone.js/index.d.ts ===
+export const x: number;
+>x : number
+
+=== /foo/zone.tsx/index.d.ts ===
+export const y: number;
+>y : number
+
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_failedLookup.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_failedLookup.trace.json
index 7561a47b1e..803520f12f 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_failedLookup.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution_withExtension_failedLookup.trace.json
@@ -6,6 +6,7 @@
     "Module name 'foo', matched pattern 'foo'.",
     "Trying substitution 'foo/foo.ts', candidate module location: 'foo/foo.ts'.",
     "File '/foo/foo.ts' does not exist.",
+    "Loading module as file / folder, candidate module location '/foo/foo.ts', target file type 'TypeScript'.",
     "Loading module 'foo' from 'node_modules' folder, target file type 'TypeScript'.",
     "Directory '/node_modules' does not exist, skipping all lookups in it.",
     "'baseUrl' option is set to '/', using this value to resolve non-relative module name 'foo'.",
@@ -13,6 +14,7 @@
     "Module name 'foo', matched pattern 'foo'.",
     "Trying substitution 'foo/foo.ts', candidate module location: 'foo/foo.ts'.",
     "File '/foo/foo.ts' does not exist.",
+    "Loading module as file / folder, candidate module location '/foo/foo.ts', target file type 'JavaScript'.",
     "Loading module 'foo' from 'node_modules' folder, target file type 'JavaScript'.",
     "Directory '/node_modules' does not exist, skipping all lookups in it.",
     "======== Module name 'foo' was not resolved. ========"
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution_withExtensionInName.ts b/tests/cases/compiler/pathMappingBasedModuleResolution_withExtensionInName.ts
new file mode 100644
index 0000000000..675003fe14
--- /dev/null
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution_withExtensionInName.ts
@@ -0,0 +1,23 @@
+// @traceResolution: true
+// @module: commonjs
+// @noImplicitReferences: true
+
+// @filename: /tsconfig.json
+{
+    "compilerOptions": {
+        "baseUrl": ".",
+        "paths": {
+            "*": ["foo/*"]
+        }
+    }
+}
+
+// @filename: /foo/zone.js/index.d.ts
+export const x: number;
+
+// @filename: /foo/zone.tsx/index.d.ts
+export const y: number;
+
+// @filename: /a.ts
+import { x } from "zone.js";
+import { y } from "zone.tsx";