diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 81d4857ad073a..74c745df1dc41 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -2465,7 +2465,7 @@ namespace ts {
             node.left.parent = node;
             node.right.parent = node;
             const lhs = node.left as PropertyAccessEntityNameExpression;
-            bindPropertyAssignment(lhs, lhs, /*isPrototypeProperty*/ false);
+            bindPropertyAssignment(lhs.expression, lhs, /*isPrototypeProperty*/ false);
         }
 
         /**
@@ -2522,7 +2522,7 @@ namespace ts {
             const isToplevel = isBinaryExpression(propertyAccess.parent)
                 ? getParentOfBinaryExpression(propertyAccess.parent).parent.kind === SyntaxKind.SourceFile
                 : propertyAccess.parent.parent.kind === SyntaxKind.SourceFile;
-            if (!isPrototypeProperty && (!namespaceSymbol || !(namespaceSymbol.flags & SymbolFlags.Namespace)) && isToplevel) {
+            if (isToplevel && !isPrototypeProperty && (!namespaceSymbol || !(namespaceSymbol.flags & SymbolFlags.Namespace))) {
                 // make symbols or add declarations for intermediate containers
                 const flags = SymbolFlags.Module | SymbolFlags.Assignment;
                 const excludeFlags = SymbolFlags.ValueModuleExcludes & ~SymbolFlags.Assignment;
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 3e9a33007261a..3b031198b38b6 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -20173,18 +20173,15 @@ namespace ts {
                 assigned || inferred;
         }
 
-        function getAssignedClassType(symbol: Symbol) {
+        function getAssignedClassType(symbol: Symbol): Type | undefined {
             const decl = symbol.valueDeclaration;
             const assignmentSymbol = decl && decl.parent &&
                 (isFunctionDeclaration(decl) && getSymbolOfNode(decl) ||
                  isBinaryExpression(decl.parent) && getSymbolOfNode(decl.parent.left) ||
                  isVariableDeclaration(decl.parent) && getSymbolOfNode(decl.parent));
-            if (assignmentSymbol) {
-                const prototype = forEach(assignmentSymbol.declarations, getAssignedJSPrototype);
-                if (prototype) {
-                    return checkExpression(prototype);
-                }
-            }
+            const prototype = assignmentSymbol && assignmentSymbol.exports && assignmentSymbol.exports.get("prototype" as __String);
+            const init = prototype && getAssignedJSPrototype(prototype.valueDeclaration);
+            return init ? checkExpression(init) : undefined;
         }
 
         function getAssignedJSPrototype(node: Node) {
diff --git a/tests/baselines/reference/typeFromPrototypeAssignment2.errors.txt b/tests/baselines/reference/typeFromPrototypeAssignment2.errors.txt
new file mode 100644
index 0000000000000..d4f66132d44a0
--- /dev/null
+++ b/tests/baselines/reference/typeFromPrototypeAssignment2.errors.txt
@@ -0,0 +1,47 @@
+tests/cases/conformance/salsa/a.js(28,24): error TS2339: Property 'addon' does not exist on type '{ set: () => void; get(): void; }'.
+
+
+==== tests/cases/conformance/salsa/a.js (1 errors) ====
+    // non top-level:
+    // all references to _map, set, get, addon should be ok
+    (function container() {
+        /** @constructor */
+        var Multimap = function() {
+            this._map = {};
+            this._map
+            this.set
+            this.get
+            this.addon
+        };
+    
+        Multimap.prototype = {
+            set: function() {
+                this._map
+                this.set
+                this.get
+                this.addon
+            },
+            get() {
+                this._map
+                this.set
+                this.get
+                this.addon
+            }
+        }
+    
+        Multimap.prototype.addon = function () {
+                           ~~~~~
+!!! error TS2339: Property 'addon' does not exist on type '{ set: () => void; get(): void; }'.
+            this._map
+            this.set
+            this.get
+            this.addon
+        }
+    
+        var mm = new Multimap();
+        mm._map
+        mm.set
+        mm.get
+        mm.addon
+    });
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/typeFromPrototypeAssignment2.symbols b/tests/baselines/reference/typeFromPrototypeAssignment2.symbols
new file mode 100644
index 0000000000000..25ae9e31c698b
--- /dev/null
+++ b/tests/baselines/reference/typeFromPrototypeAssignment2.symbols
@@ -0,0 +1,127 @@
+=== tests/cases/conformance/salsa/a.js ===
+// non top-level:
+// all references to _map, set, get, addon should be ok
+(function container() {
+>container : Symbol(container, Decl(a.js, 2, 1))
+
+    /** @constructor */
+    var Multimap = function() {
+>Multimap : Symbol(Multimap, Decl(a.js, 4, 7))
+
+        this._map = {};
+>this._map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+>_map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+
+        this._map
+>this._map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+>_map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+
+        this.set
+>this.set : Symbol(set, Decl(a.js, 12, 26))
+>set : Symbol(set, Decl(a.js, 12, 26))
+
+        this.get
+>this.get : Symbol(get, Decl(a.js, 18, 10))
+>get : Symbol(get, Decl(a.js, 18, 10))
+
+        this.addon
+>this.addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+>addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+
+    };
+
+    Multimap.prototype = {
+>Multimap.prototype : Symbol(Multimap.prototype, Decl(a.js, 10, 6))
+>Multimap : Symbol(Multimap, Decl(a.js, 4, 7))
+>prototype : Symbol(Multimap.prototype, Decl(a.js, 10, 6))
+
+        set: function() {
+>set : Symbol(set, Decl(a.js, 12, 26))
+
+            this._map
+>this._map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+>_map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+
+            this.set
+>this.set : Symbol(set, Decl(a.js, 12, 26))
+>set : Symbol(set, Decl(a.js, 12, 26))
+
+            this.get
+>this.get : Symbol(get, Decl(a.js, 18, 10))
+>get : Symbol(get, Decl(a.js, 18, 10))
+
+            this.addon
+>this.addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+>addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+
+        },
+        get() {
+>get : Symbol(get, Decl(a.js, 18, 10))
+
+            this._map
+>this._map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+>_map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+
+            this.set
+>this.set : Symbol(set, Decl(a.js, 12, 26))
+>set : Symbol(set, Decl(a.js, 12, 26))
+
+            this.get
+>this.get : Symbol(get, Decl(a.js, 18, 10))
+>get : Symbol(get, Decl(a.js, 18, 10))
+
+            this.addon
+>this.addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+>addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+        }
+    }
+
+    Multimap.prototype.addon = function () {
+>Multimap.prototype : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+>Multimap : Symbol(Multimap, Decl(a.js, 4, 7))
+>prototype : Symbol(Multimap.prototype, Decl(a.js, 10, 6))
+>addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+
+        this._map
+>this._map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+>_map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+
+        this.set
+>this.set : Symbol(set, Decl(a.js, 12, 26))
+>set : Symbol(set, Decl(a.js, 12, 26))
+
+        this.get
+>this.get : Symbol(get, Decl(a.js, 18, 10))
+>get : Symbol(get, Decl(a.js, 18, 10))
+
+        this.addon
+>this.addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+>addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+    }
+
+    var mm = new Multimap();
+>mm : Symbol(mm, Decl(a.js, 34, 7))
+>Multimap : Symbol(Multimap, Decl(a.js, 4, 7))
+
+    mm._map
+>mm._map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+>mm : Symbol(mm, Decl(a.js, 34, 7))
+>_map : Symbol(Multimap._map, Decl(a.js, 4, 31))
+
+    mm.set
+>mm.set : Symbol(set, Decl(a.js, 12, 26))
+>mm : Symbol(mm, Decl(a.js, 34, 7))
+>set : Symbol(set, Decl(a.js, 12, 26))
+
+    mm.get
+>mm.get : Symbol(get, Decl(a.js, 18, 10))
+>mm : Symbol(mm, Decl(a.js, 34, 7))
+>get : Symbol(get, Decl(a.js, 18, 10))
+
+    mm.addon
+>mm.addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+>mm : Symbol(mm, Decl(a.js, 34, 7))
+>addon : Symbol(Multimap.addon, Decl(a.js, 25, 5))
+
+});
+
diff --git a/tests/baselines/reference/typeFromPrototypeAssignment2.types b/tests/baselines/reference/typeFromPrototypeAssignment2.types
new file mode 100644
index 0000000000000..d37f421a356e8
--- /dev/null
+++ b/tests/baselines/reference/typeFromPrototypeAssignment2.types
@@ -0,0 +1,156 @@
+=== tests/cases/conformance/salsa/a.js ===
+// non top-level:
+// all references to _map, set, get, addon should be ok
+(function container() {
+>(function container() {    /** @constructor */    var Multimap = function() {        this._map = {};        this._map        this.set        this.get        this.addon    };    Multimap.prototype = {        set: function() {            this._map            this.set            this.get            this.addon        },        get() {            this._map            this.set            this.get            this.addon        }    }    Multimap.prototype.addon = function () {        this._map        this.set        this.get        this.addon    }    var mm = new Multimap();    mm._map    mm.set    mm.get    mm.addon}) : () => void
+>function container() {    /** @constructor */    var Multimap = function() {        this._map = {};        this._map        this.set        this.get        this.addon    };    Multimap.prototype = {        set: function() {            this._map            this.set            this.get            this.addon        },        get() {            this._map            this.set            this.get            this.addon        }    }    Multimap.prototype.addon = function () {        this._map        this.set        this.get        this.addon    }    var mm = new Multimap();    mm._map    mm.set    mm.get    mm.addon} : () => void
+>container : () => void
+
+    /** @constructor */
+    var Multimap = function() {
+>Multimap : typeof Multimap
+>function() {        this._map = {};        this._map        this.set        this.get        this.addon    } : typeof Multimap
+
+        this._map = {};
+>this._map = {} : {}
+>this._map : {}
+>this : Multimap & { set: () => void; get(): void; }
+>_map : {}
+>{} : {}
+
+        this._map
+>this._map : {}
+>this : Multimap & { set: () => void; get(): void; }
+>_map : {}
+
+        this.set
+>this.set : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>set : () => void
+
+        this.get
+>this.get : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>get : () => void
+
+        this.addon
+>this.addon : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>addon : () => void
+
+    };
+
+    Multimap.prototype = {
+>Multimap.prototype = {        set: function() {            this._map            this.set            this.get            this.addon        },        get() {            this._map            this.set            this.get            this.addon        }    } : { set: () => void; get(): void; }
+>Multimap.prototype : { set: () => void; get(): void; }
+>Multimap : typeof Multimap
+>prototype : { set: () => void; get(): void; }
+>{        set: function() {            this._map            this.set            this.get            this.addon        },        get() {            this._map            this.set            this.get            this.addon        }    } : { set: () => void; get(): void; }
+
+        set: function() {
+>set : () => void
+>function() {            this._map            this.set            this.get            this.addon        } : () => void
+
+            this._map
+>this._map : {}
+>this : Multimap & { set: () => void; get(): void; }
+>_map : {}
+
+            this.set
+>this.set : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>set : () => void
+
+            this.get
+>this.get : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>get : () => void
+
+            this.addon
+>this.addon : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>addon : () => void
+
+        },
+        get() {
+>get : () => void
+
+            this._map
+>this._map : {}
+>this : Multimap & { set: () => void; get(): void; }
+>_map : {}
+
+            this.set
+>this.set : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>set : () => void
+
+            this.get
+>this.get : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>get : () => void
+
+            this.addon
+>this.addon : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>addon : () => void
+        }
+    }
+
+    Multimap.prototype.addon = function () {
+>Multimap.prototype.addon = function () {        this._map        this.set        this.get        this.addon    } : () => void
+>Multimap.prototype.addon : any
+>Multimap.prototype : { set: () => void; get(): void; }
+>Multimap : typeof Multimap
+>prototype : { set: () => void; get(): void; }
+>addon : any
+>function () {        this._map        this.set        this.get        this.addon    } : () => void
+
+        this._map
+>this._map : {}
+>this : Multimap & { set: () => void; get(): void; }
+>_map : {}
+
+        this.set
+>this.set : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>set : () => void
+
+        this.get
+>this.get : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>get : () => void
+
+        this.addon
+>this.addon : () => void
+>this : Multimap & { set: () => void; get(): void; }
+>addon : () => void
+    }
+
+    var mm = new Multimap();
+>mm : Multimap & { set: () => void; get(): void; }
+>new Multimap() : Multimap & { set: () => void; get(): void; }
+>Multimap : typeof Multimap
+
+    mm._map
+>mm._map : {}
+>mm : Multimap & { set: () => void; get(): void; }
+>_map : {}
+
+    mm.set
+>mm.set : () => void
+>mm : Multimap & { set: () => void; get(): void; }
+>set : () => void
+
+    mm.get
+>mm.get : () => void
+>mm : Multimap & { set: () => void; get(): void; }
+>get : () => void
+
+    mm.addon
+>mm.addon : () => void
+>mm : Multimap & { set: () => void; get(): void; }
+>addon : () => void
+
+});
+
diff --git a/tests/cases/conformance/salsa/typeFromPrototypeAssignment2.ts b/tests/cases/conformance/salsa/typeFromPrototypeAssignment2.ts
new file mode 100644
index 0000000000000..68966c923d5c8
--- /dev/null
+++ b/tests/cases/conformance/salsa/typeFromPrototypeAssignment2.ts
@@ -0,0 +1,46 @@
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+// @Filename: a.js
+// @strict: true
+
+// non top-level:
+// all references to _map, set, get, addon should be ok
+(function container() {
+    /** @constructor */
+    var Multimap = function() {
+        this._map = {};
+        this._map
+        this.set
+        this.get
+        this.addon
+    };
+
+    Multimap.prototype = {
+        set: function() {
+            this._map
+            this.set
+            this.get
+            this.addon
+        },
+        get() {
+            this._map
+            this.set
+            this.get
+            this.addon
+        }
+    }
+
+    Multimap.prototype.addon = function () {
+        this._map
+        this.set
+        this.get
+        this.addon
+    }
+
+    var mm = new Multimap();
+    mm._map
+    mm.set
+    mm.get
+    mm.addon
+});