diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index ad6f1a811e..0e169ca7ac 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -1435,7 +1435,8 @@ namespace ts {
             // Declare a 'member' in case it turns out the container was an ES5 class
             if (container.kind === SyntaxKind.FunctionExpression || container.kind === SyntaxKind.FunctionDeclaration) {
                 container.symbol.members = container.symbol.members || {};
-                declareSymbol(container.symbol.members, container.symbol, node, SymbolFlags.Property, SymbolFlags.PropertyExcludes);
+                // It's acceptable for multiple 'this' assignments of the same identifier to occur
+                declareSymbol(container.symbol.members, container.symbol, node, SymbolFlags.Property, SymbolFlags.PropertyExcludes & ~SymbolFlags.Property);
             }
         }
 
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 929453a90e..a66af2ab3b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2837,7 +2837,7 @@ namespace ts {
                 }
                 // Handle module.exports = expr
                 if (declaration.kind === SyntaxKind.BinaryExpression) {
-                    return links.type = checkExpression((<BinaryExpression>declaration).right);
+                    return links.type = getUnionType(map(symbol.declarations, (decl: BinaryExpression) => checkExpressionCached(decl.right)));
                 }
                 if (declaration.kind === SyntaxKind.PropertyAccessExpression) {
                     // Declarations only exist for property access expressions for certain
diff --git a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics23.ts b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics23.ts
new file mode 100644
index 0000000000..2524e50e66
--- /dev/null
+++ b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics23.ts
@@ -0,0 +1,14 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @Filename: a.js
+//// function Person(age) {
+////     if (age >= 18) {
+////         this.canVote = true;
+////     } else {
+////         this.canVote = false;
+////     }
+//// }
+
+verify.getSyntacticDiagnostics(`[]`);
+verify.getSemanticDiagnostics(`[]`);
diff --git a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics24.ts b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics24.ts
new file mode 100644
index 0000000000..cf70f883e9
--- /dev/null
+++ b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics24.ts
@@ -0,0 +1,16 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @Filename: a.js
+//// function Person(age) {
+////     if (age >= 18) {
+////         this.canVote = true;
+////     } else {
+////         this.canVote = 23;
+////     }
+//// }
+//// let x = new Person(100);
+//// x.canVote/**/;
+
+goTo.marker();
+verify.quickInfoIs('(property) Person.canVote: boolean | number');