diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 0e0b9a53b5d9c..6b42589471f1e 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -8229,7 +8229,7 @@ namespace Parser {
         // If we are parsing a dotted namespace name, we want to
         // propagate the 'Namespace' flag across the names if set.
         const namespaceFlag = flags & NodeFlags.Namespace;
-        const name = parseIdentifier();
+        const name = flags & NodeFlags.NestedNamespace ? parseIdentifierName() : parseIdentifier();
         const body = parseOptional(SyntaxKind.DotToken)
             ? parseModuleOrNamespaceDeclaration(getNodePos(), /*hasJSDoc*/ false, /*modifiers*/ undefined, NodeFlags.NestedNamespace | namespaceFlag) as NamespaceDeclaration
             : parseModuleBlock();
diff --git a/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.errors.txt b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.errors.txt
new file mode 100644
index 0000000000000..32d0fa85f966d
--- /dev/null
+++ b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.errors.txt
@@ -0,0 +1,27 @@
+ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts(11,1): error TS2304: Cannot find name 'declare'.
+ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts(11,9): error TS2580: Cannot find name 'module'. Do you need to install type definitions for node? Try `npm i --save-dev @types/node`.
+ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts(11,16): error TS2819: Namespace name cannot be 'debugger'.
+ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts(11,25): error TS1005: ';' expected.
+
+
+==== ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts (4 errors) ====
+    // https://github.com/microsoft/TypeScript/issues/7840
+    
+    declare module chrome.debugger {
+        declare var tabId: number;
+    }
+    
+    export const tabId = chrome.debugger.tabId;
+    
+    declare module test.class {}
+    
+    declare module debugger {} // still an error
+    ~~~~~~~
+!!! error TS2304: Cannot find name 'declare'.
+            ~~~~~~
+!!! error TS2580: Cannot find name 'module'. Do you need to install type definitions for node? Try `npm i --save-dev @types/node`.
+                   ~~~~~~~~
+!!! error TS2819: Namespace name cannot be 'debugger'.
+                            ~
+!!! error TS1005: ';' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.js b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.js
new file mode 100644
index 0000000000000..8066fd7de6b57
--- /dev/null
+++ b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.js
@@ -0,0 +1,30 @@
+//// [tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts] ////
+
+//// [ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts]
+// https://github.com/microsoft/TypeScript/issues/7840
+
+declare module chrome.debugger {
+    declare var tabId: number;
+}
+
+export const tabId = chrome.debugger.tabId;
+
+declare module test.class {}
+
+declare module debugger {} // still an error
+
+
+//// [ambientModuleDeclarationWithReservedIdentifierInDottedPath.js]
+"use strict";
+// https://github.com/microsoft/TypeScript/issues/7840
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.tabId = void 0;
+exports.tabId = chrome.debugger.tabId;
+declare;
+module;
+debugger;
+{ } // still an error
+
+
+//// [ambientModuleDeclarationWithReservedIdentifierInDottedPath.d.ts]
+export declare const tabId: number;
diff --git a/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.symbols b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.symbols
new file mode 100644
index 0000000000000..353e1d3c7e1e7
--- /dev/null
+++ b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.symbols
@@ -0,0 +1,27 @@
+//// [tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts] ////
+
+=== ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts ===
+// https://github.com/microsoft/TypeScript/issues/7840
+
+declare module chrome.debugger {
+>chrome : Symbol(chrome, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 0, 0))
+>debugger : Symbol(debugger, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 2, 22))
+
+    declare var tabId: number;
+>tabId : Symbol(tabId, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 3, 15))
+}
+
+export const tabId = chrome.debugger.tabId;
+>tabId : Symbol(tabId, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 6, 12))
+>chrome.debugger.tabId : Symbol(chrome.debugger.tabId, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 3, 15))
+>chrome.debugger : Symbol(chrome.debugger, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 2, 22))
+>chrome : Symbol(chrome, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 0, 0))
+>debugger : Symbol(chrome.debugger, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 2, 22))
+>tabId : Symbol(chrome.debugger.tabId, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 3, 15))
+
+declare module test.class {}
+>test : Symbol(test, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 6, 43))
+>class : Symbol(class, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts, 8, 20))
+
+declare module debugger {} // still an error
+
diff --git a/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.types b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.types
new file mode 100644
index 0000000000000..d3d2470edc09d
--- /dev/null
+++ b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath.types
@@ -0,0 +1,27 @@
+//// [tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts] ////
+
+=== ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts ===
+// https://github.com/microsoft/TypeScript/issues/7840
+
+declare module chrome.debugger {
+>chrome : typeof chrome
+>debugger : typeof debugger
+
+    declare var tabId: number;
+>tabId : number
+}
+
+export const tabId = chrome.debugger.tabId;
+>tabId : number
+>chrome.debugger.tabId : number
+>chrome.debugger : typeof chrome.debugger
+>chrome : typeof chrome
+>debugger : typeof chrome.debugger
+>tabId : number
+
+declare module test.class {}
+
+declare module debugger {} // still an error
+>declare : any
+>module : any
+
diff --git a/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.errors.txt b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.errors.txt
new file mode 100644
index 0000000000000..3cce670b6fc12
--- /dev/null
+++ b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.errors.txt
@@ -0,0 +1,25 @@
+ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts(9,1): error TS2304: Cannot find name 'declare'.
+ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts(9,9): error TS2304: Cannot find name 'namespace'.
+ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts(9,19): error TS2819: Namespace name cannot be 'debugger'.
+ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts(9,28): error TS1005: ';' expected.
+
+
+==== ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts (4 errors) ====
+    declare namespace chrome.debugger {
+        declare var tabId: number;
+    }
+    
+    export const tabId = chrome.debugger.tabId;
+    
+    declare namespace test.class {}
+    
+    declare namespace debugger {} // still an error
+    ~~~~~~~
+!!! error TS2304: Cannot find name 'declare'.
+            ~~~~~~~~~
+!!! error TS2304: Cannot find name 'namespace'.
+                      ~~~~~~~~
+!!! error TS2819: Namespace name cannot be 'debugger'.
+                               ~
+!!! error TS1005: ';' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.js b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.js
new file mode 100644
index 0000000000000..1751a8d5c967e
--- /dev/null
+++ b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.js
@@ -0,0 +1,27 @@
+//// [tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts] ////
+
+//// [ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts]
+declare namespace chrome.debugger {
+    declare var tabId: number;
+}
+
+export const tabId = chrome.debugger.tabId;
+
+declare namespace test.class {}
+
+declare namespace debugger {} // still an error
+
+
+//// [ambientModuleDeclarationWithReservedIdentifierInDottedPath2.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.tabId = void 0;
+exports.tabId = chrome.debugger.tabId;
+declare;
+namespace;
+debugger;
+{ } // still an error
+
+
+//// [ambientModuleDeclarationWithReservedIdentifierInDottedPath2.d.ts]
+export declare const tabId: number;
diff --git a/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.symbols b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.symbols
new file mode 100644
index 0000000000000..2b61ab650343f
--- /dev/null
+++ b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.symbols
@@ -0,0 +1,25 @@
+//// [tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts] ////
+
+=== ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts ===
+declare namespace chrome.debugger {
+>chrome : Symbol(chrome, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 0, 0))
+>debugger : Symbol(debugger, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 0, 25))
+
+    declare var tabId: number;
+>tabId : Symbol(tabId, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 1, 15))
+}
+
+export const tabId = chrome.debugger.tabId;
+>tabId : Symbol(tabId, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 4, 12))
+>chrome.debugger.tabId : Symbol(chrome.debugger.tabId, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 1, 15))
+>chrome.debugger : Symbol(chrome.debugger, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 0, 25))
+>chrome : Symbol(chrome, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 0, 0))
+>debugger : Symbol(chrome.debugger, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 0, 25))
+>tabId : Symbol(chrome.debugger.tabId, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 1, 15))
+
+declare namespace test.class {}
+>test : Symbol(test, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 4, 43))
+>class : Symbol(class, Decl(ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts, 6, 23))
+
+declare namespace debugger {} // still an error
+
diff --git a/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.types b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.types
new file mode 100644
index 0000000000000..57367d2f26bcd
--- /dev/null
+++ b/tests/baselines/reference/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.types
@@ -0,0 +1,25 @@
+//// [tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts] ////
+
+=== ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts ===
+declare namespace chrome.debugger {
+>chrome : typeof chrome
+>debugger : typeof debugger
+
+    declare var tabId: number;
+>tabId : number
+}
+
+export const tabId = chrome.debugger.tabId;
+>tabId : number
+>chrome.debugger.tabId : number
+>chrome.debugger : typeof chrome.debugger
+>chrome : typeof chrome
+>debugger : typeof chrome.debugger
+>tabId : number
+
+declare namespace test.class {}
+
+declare namespace debugger {} // still an error
+>declare : any
+>namespace : any
+
diff --git a/tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts b/tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts
new file mode 100644
index 0000000000000..5871010878546
--- /dev/null
+++ b/tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath.ts
@@ -0,0 +1,13 @@
+// @declaration: true
+
+// https://github.com/microsoft/TypeScript/issues/7840
+
+declare module chrome.debugger {
+    declare var tabId: number;
+}
+
+export const tabId = chrome.debugger.tabId;
+
+declare module test.class {}
+
+declare module debugger {} // still an error
diff --git a/tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts b/tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts
new file mode 100644
index 0000000000000..7b41511cb2cb9
--- /dev/null
+++ b/tests/cases/conformance/ambient/ambientModuleDeclarationWithReservedIdentifierInDottedPath2.ts
@@ -0,0 +1,11 @@
+// @declaration: true
+
+declare namespace chrome.debugger {
+    declare var tabId: number;
+}
+
+export const tabId = chrome.debugger.tabId;
+
+declare namespace test.class {}
+
+declare namespace debugger {} // still an error