diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ae44d873861..18ec5bf9d6d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -20459,7 +20459,7 @@ namespace ts {
                  isBinaryExpression(decl.parent) && getSymbolOfNode(decl.parent.left) ||
                  isVariableDeclaration(decl.parent) && getSymbolOfNode(decl.parent));
             const prototype = assignmentSymbol && assignmentSymbol.exports && assignmentSymbol.exports.get("prototype" as __String);
-            const init = prototype && getAssignedJSPrototype(prototype.valueDeclaration);
+            const init = prototype && prototype.valueDeclaration && getAssignedJSPrototype(prototype.valueDeclaration);
             return init ? checkExpression(init) : undefined;
         }
 
diff --git a/tests/baselines/reference/constructorFunctionMergeWithClass.symbols b/tests/baselines/reference/constructorFunctionMergeWithClass.symbols
new file mode 100644
index 00000000000..ecc45e94054
--- /dev/null
+++ b/tests/baselines/reference/constructorFunctionMergeWithClass.symbols
@@ -0,0 +1,21 @@
+=== tests/cases/conformance/salsa/file1.js ===
+var SomeClass = function () {
+>SomeClass : Symbol(SomeClass, Decl(file1.js, 0, 3), Decl(file2.js, 0, 0), Decl(file2.js, 0, 19))
+
+    this.otherProp = 0;
+>otherProp : Symbol(SomeClass.otherProp, Decl(file1.js, 0, 29))
+
+};
+
+new SomeClass();
+>SomeClass : Symbol(SomeClass, Decl(file1.js, 0, 3), Decl(file2.js, 0, 0), Decl(file2.js, 0, 19))
+
+=== tests/cases/conformance/salsa/file2.js ===
+class SomeClass { }
+>SomeClass : Symbol(SomeClass, Decl(file1.js, 0, 3), Decl(file2.js, 0, 0), Decl(file2.js, 0, 19))
+
+SomeClass.prop = 0
+>SomeClass.prop : Symbol(SomeClass.prop, Decl(file2.js, 0, 19))
+>SomeClass : Symbol(SomeClass, Decl(file1.js, 0, 3), Decl(file2.js, 0, 0), Decl(file2.js, 0, 19))
+>prop : Symbol(SomeClass.prop, Decl(file2.js, 0, 19))
+
diff --git a/tests/baselines/reference/constructorFunctionMergeWithClass.types b/tests/baselines/reference/constructorFunctionMergeWithClass.types
new file mode 100644
index 00000000000..7bed55aacce
--- /dev/null
+++ b/tests/baselines/reference/constructorFunctionMergeWithClass.types
@@ -0,0 +1,29 @@
+=== tests/cases/conformance/salsa/file1.js ===
+var SomeClass = function () {
+>SomeClass : typeof SomeClass
+>function () {    this.otherProp = 0;} : typeof SomeClass
+
+    this.otherProp = 0;
+>this.otherProp = 0 : 0
+>this.otherProp : any
+>this : any
+>otherProp : any
+>0 : 0
+
+};
+
+new SomeClass();
+>new SomeClass() : SomeClass
+>SomeClass : typeof SomeClass
+
+=== tests/cases/conformance/salsa/file2.js ===
+class SomeClass { }
+>SomeClass : SomeClass
+
+SomeClass.prop = 0
+>SomeClass.prop = 0 : 0
+>SomeClass.prop : number
+>SomeClass : typeof SomeClass
+>prop : number
+>0 : 0
+
diff --git a/tests/cases/conformance/salsa/constructorFunctionMergeWithClass.ts b/tests/cases/conformance/salsa/constructorFunctionMergeWithClass.ts
new file mode 100644
index 00000000000..b6a0a50f029
--- /dev/null
+++ b/tests/cases/conformance/salsa/constructorFunctionMergeWithClass.ts
@@ -0,0 +1,14 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+
+// @Filename: file1.js
+var SomeClass = function () {
+    this.otherProp = 0;
+};
+
+new SomeClass();
+
+// @Filename: file2.js
+class SomeClass { }
+SomeClass.prop = 0