diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 5370e7c4f02..033614d2b41 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6369,7 +6369,7 @@ namespace ts {
                     // Assumed result is true. If check was not for a primitive type, remove all primitive types
                     if (!typeInfo) {
                         return removeTypesFromUnionType(type, /*typeKind*/ TypeFlags.StringLike | TypeFlags.NumberLike | TypeFlags.Boolean | TypeFlags.ESSymbol,
-                            /*isOfTypeKind*/ true, /*allowEmptyUnionResult*/ false);
+                            /*isOfTypeKind*/ true, /*allowEmptyUnionResult*/ true);
                     }
                     // Check was for a primitive type, return that primitive type if it is a subtype
                     if (isTypeSubtypeOf(typeInfo.type, type)) {
@@ -6377,12 +6377,12 @@ namespace ts {
                     }
                     // Otherwise, remove all types that aren't of the primitive type kind. This can happen when the type is
                     // union of enum types and other types.
-                    return removeTypesFromUnionType(type, /*typeKind*/ typeInfo.flags, /*isOfTypeKind*/ false, /*allowEmptyUnionResult*/ false);
+                    return removeTypesFromUnionType(type, /*typeKind*/ typeInfo.flags, /*isOfTypeKind*/ false, /*allowEmptyUnionResult*/ true);
                 }
                 else {
                     // Assumed result is false. If check was for a primitive type, remove that primitive type
                     if (typeInfo) {
-                        return removeTypesFromUnionType(type, /*typeKind*/ typeInfo.flags, /*isOfTypeKind*/ true, /*allowEmptyUnionResult*/ false);
+                        return removeTypesFromUnionType(type, /*typeKind*/ typeInfo.flags, /*isOfTypeKind*/ true, /*allowEmptyUnionResult*/ true);
                     }
                     // Otherwise we don't have enough information to do anything.
                     return type;
diff --git a/tests/cases/conformance/expressions/typeGuards/typeGuardNesting.ts b/tests/cases/conformance/expressions/typeGuards/typeGuardNesting.ts
new file mode 100644
index 00000000000..b06b5880800
--- /dev/null
+++ b/tests/cases/conformance/expressions/typeGuards/typeGuardNesting.ts
@@ -0,0 +1,4 @@
+let strOrBool: string|boolean;
+if ((typeof strOrBool === 'boolean' && !strOrBool) || typeof strOrBool === 'string') {
+	var label: string = (typeof strOrBool === 'string') ? strOrBool : "other string";
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/expressions/typeGuards/typeGuardRedundancy.ts b/tests/cases/conformance/expressions/typeGuards/typeGuardRedundancy.ts
new file mode 100644
index 00000000000..4e9e3137d78
--- /dev/null
+++ b/tests/cases/conformance/expressions/typeGuards/typeGuardRedundancy.ts
@@ -0,0 +1,9 @@
+var x: string|number;
+
+var r1 = typeof x === "string" && typeof x === "string" ? x.substr : x.toFixed;
+
+var r2 = !(typeof x === "string" && typeof x === "string") ? x.toFixed : x.substr;
+
+var r3 = typeof x === "string" || typeof x === "string" ? x.substr : x.toFixed;
+
+var r4 = !(typeof x === "string" || typeof x === "string") ? x.toFixed : x.substr;
\ No newline at end of file