diff --git a/src/compiler/operation-typer.cc b/src/compiler/operation-typer.cc
index 40eb88a036b4..46d6557b2117 100644
--- a/src/compiler/operation-typer.cc
+++ b/src/compiler/operation-typer.cc
@@ -476,8 +476,9 @@ Type* OperationTyper::NumberTanh(Type* type) {
 Type* OperationTyper::NumberTrunc(Type* type) {
   DCHECK(type->Is(Type::Number()));
   if (type->Is(cache_.kIntegerOrMinusZeroOrNaN)) return type;
-  // TODO(bmeurer): We could infer a more precise type here.
-  return cache_.kIntegerOrMinusZeroOrNaN;
+  type = Type::Intersect(type, Type::NaN(), zone());
+  type = Type::Union(type, cache_.kIntegerOrMinusZero, zone());
+  return type;
 }
 
 Type* OperationTyper::NumberToBoolean(Type* type) {
diff --git a/test/mjsunit/compiler/math-trunc.js b/test/mjsunit/compiler/math-trunc.js
new file mode 100644
index 000000000000..e5cc523bc0ec
--- /dev/null
+++ b/test/mjsunit/compiler/math-trunc.js
@@ -0,0 +1,39 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+// Ensure that the typing rule for Math.trunc deals correctly with
+// inputs in the range (-1.0,0.0), which are mapped to -0.
+(function() {
+  function foo(x) {
+    // Arrange x such that TurboFan infers type PlainNumber \/ NaN.
+    x = +x;
+    x = Math.abs(x) - 1.0;
+    return Object.is(-0, Math.trunc(x));
+  }
+
+  assertFalse(foo(1.5));
+  assertTrue(foo(0.5));
+  %OptimizeFunctionOnNextCall(foo);
+  assertFalse(foo(1.5));
+  assertTrue(foo(0.5));
+})();
+
+// Ensure that the typing rule for Math.trunc deals correctly with
+// NaN inputs, which are mapped to NaN.
+(function() {
+  function foo(x) {
+    // Arrange x such that TurboFan infers type PlainNumber \/ NaN.
+    x = +x;
+    x = Math.abs(x) - 1.0;
+    return Object.is(NaN, Math.trunc(x));
+  }
+
+  assertFalse(foo(1.5));
+  assertTrue(foo(NaN));
+  %OptimizeFunctionOnNextCall(foo);
+  assertFalse(foo(1.5));
+  assertTrue(foo(NaN));
+})();