diff --git a/source/maths/Fixed.h b/source/maths/Fixed.h
index 859fba99c3..b1f170891d 100644
--- a/source/maths/Fixed.h
+++ b/source/maths/Fixed.h
@@ -92,6 +92,12 @@ inline T round_away_from_zero(float value)
 	return (T)(value >= 0 ? value + 0.5f : value - 0.5f);
 }
 
+template <typename T>
+inline T round_away_from_zero(double value)
+{
+	return (T)(value >= 0 ? value + 0.5 : value - 0.5);
+}
+
 /**
  * A simple fixed-point number class.
  *
diff --git a/source/scriptinterface/tests/test_ScriptConversions.h b/source/scriptinterface/tests/test_ScriptConversions.h
index d47af09390..a9154f9e45 100644
--- a/source/scriptinterface/tests/test_ScriptConversions.h
+++ b/source/scriptinterface/tests/test_ScriptConversions.h
@@ -47,7 +47,7 @@ class TestScriptConversions : public CxxTest::TestSuite
 	}
 
 	template <typename T>
-	void roundtrip(const T& value, const std::string& expected)
+	void roundtrip(const T& value, const char* expected)
 	{
 		ScriptInterface script("Test");
 		JSContext* cx = script.GetContext();
@@ -58,7 +58,8 @@ class TestScriptConversions : public CxxTest::TestSuite
 		std::string source;
 		TS_ASSERT(script.CallFunction(OBJECT_TO_JSVAL(JS_GetGlobalObject(cx)), "uneval", CScriptVal(v1), source));
 
-		TS_ASSERT_STR_EQUALS(source, expected);
+		if (expected)
+			TS_ASSERT_STR_EQUALS(source, expected);
 
 		T v2 = T();
 		TS_ASSERT(ScriptInterface::FromJSVal(script.GetContext(), v1, v2));
@@ -160,4 +161,23 @@ public:
 	}
 
 	// TODO: test vectors
+
+	void test_fixed()
+	{
+		// NOTE: fixed conversions are defined in simulation2/scripting/EngineScriptConversions.cpp
+
+		fixed f;
+
+		f.SetInternalValue(10590283);
+		roundtrip<fixed>(f, "161.5948944091797");
+
+		f.SetInternalValue(-10590283);
+		roundtrip<fixed>(f, "-161.5948944091797");
+
+		f.SetInternalValue(2000000000);
+		roundtrip<fixed>(f, "30517.578125");
+
+		f.SetInternalValue(2000000001);
+		roundtrip<fixed>(f, "30517.57814025879");
+	}
 };
diff --git a/source/simulation2/scripting/EngineScriptConversions.cpp b/source/simulation2/scripting/EngineScriptConversions.cpp
index 95d9e8458c..0053dc97ca 100644
--- a/source/simulation2/scripting/EngineScriptConversions.cpp
+++ b/source/simulation2/scripting/EngineScriptConversions.cpp
@@ -186,7 +186,8 @@ template<> bool ScriptInterface::FromJSVal<fixed>(JSContext* cx, jsval v, fixed&
 	if (!JS_ValueToNumber(cx, v, &ret))
 		return false;
 	out = fixed::FromDouble(ret);
-	// TODO: ought to check that this conversion is consistent and portable
+	// double can precisely represent the full range of fixed, so this is a non-lossy conversion
+
 	return true;
 }
 
@@ -194,7 +195,6 @@ template<> jsval ScriptInterface::ToJSVal<fixed>(JSContext* cx, const fixed& val
 {
 	jsval rval = JSVAL_VOID;
 	JS_NewNumberValue(cx, val.ToDouble(), &rval); // ignore return value
-	// TODO: ought to check that this conversion is consistent and portable
 	return rval;
 }