diff --git a/lib/VM/JSLib/Function.cpp b/lib/VM/JSLib/Function.cpp
index 3d2bf9bdb4f..0672bd3ef95 100644
--- a/lib/VM/JSLib/Function.cpp
+++ b/lib/VM/JSLib/Function.cpp
@@ -143,7 +143,7 @@ functionPrototypeToString(void *, Runtime *runtime, NativeArgs args) {
   // Extract the name.
   auto propRes = JSObject::getNamed_RJS(
       func, runtime, Predefined::getSymbolID(Predefined::name));
-  if (propRes == ExecutionStatus::EXCEPTION) {
+  if (LLVM_UNLIKELY(propRes == ExecutionStatus::EXCEPTION)) {
     return ExecutionStatus::EXCEPTION;
   }
 
@@ -151,39 +151,43 @@ functionPrototypeToString(void *, Runtime *runtime, NativeArgs args) {
   if (!(*propRes)->isUndefined()) {
     auto strRes =
         toString_RJS(runtime, runtime->makeHandle(std::move(*propRes)));
-    if (strRes == ExecutionStatus::EXCEPTION) {
+    if (LLVM_UNLIKELY(strRes == ExecutionStatus::EXCEPTION)) {
       return ExecutionStatus::EXCEPTION;
     }
     strRes->get()->appendUTF16String(strBuf);
   }
 
-  // Append the named parameters.
-  strBuf.append('(');
-
-  // Extract ".length".
-  auto lengthProp = Callable::extractOwnLengthProperty_RJS(func, runtime);
-  if (lengthProp == ExecutionStatus::EXCEPTION)
-    return ExecutionStatus::EXCEPTION;
+  // Formal parameters and the rest of the body.
+  if (vmisa<NativeFunction>(*func)) {
+    // Use [native code] here because we want to work with tools like Babel
+    // which detect the string "[native code]" and use it to alter behavior
+    // during the class transform.
+    // Also print without synthesized formal parameters to avoid breaking
+    // heuristics that detect the string "() { [native code] }".
+    // \see https://github.com/facebook/hermes/issues/471
+    strBuf.append("() { [native code] }");
+  } else {
+    // Append the synthesized formal parameters.
+    strBuf.append('(');
 
-  // The value of the property is not guaranteed to be meaningful, so clamp it
-  // to [0..65535] for sanity.
-  uint32_t paramCount = (uint32_t)std::min(65535.0, std::max(0.0, *lengthProp));
+    // Extract ".length".
+    auto lengthProp = Callable::extractOwnLengthProperty_RJS(func, runtime);
+    if (lengthProp == ExecutionStatus::EXCEPTION)
+      return ExecutionStatus::EXCEPTION;
 
-  for (uint32_t i = 0; i < paramCount; ++i) {
-    if (i != 0)
-      strBuf.append(", ");
-    char buf[16];
-    ::snprintf(buf, sizeof(buf), "a%u", i);
-    strBuf.append(buf);
-  }
+    // The value of the property is not guaranteed to be meaningful, so clamp it
+    // to [0..65535] for sanity.
+    uint32_t paramCount =
+        (uint32_t)std::min(65535.0, std::max(0.0, *lengthProp));
+
+    for (uint32_t i = 0; i < paramCount; ++i) {
+      if (i != 0)
+        strBuf.append(", ");
+      char buf[16];
+      ::snprintf(buf, sizeof(buf), "a%u", i);
+      strBuf.append(buf);
+    }
 
-  // The rest of the body.
-  if (vmisa<NativeFunction>(*func)) {
-    // Use [native code] here because we want to work with tools like
-    // Babel which detect the string [native code] and use it to alter
-    // behavior during the class transform.
-    strBuf.append(") { [native code] }");
-  } else {
     // Avoid using the [native code] string to prevent extra wrapping overhead
     // in, e.g., Babel's class extension mechanism.
     strBuf.append(") { [bytecode] }");
diff --git a/test/hermes/function-constructor.js b/test/hermes/function-constructor.js
index 219d26bc293..f5a5c7f5ef8 100644
--- a/test/hermes/function-constructor.js
+++ b/test/hermes/function-constructor.js
@@ -55,8 +55,12 @@ print(function(a,b,c){});
 // CHECK-NEXT: function (a0, a1, a2) { [bytecode] }
 print(function(a,b,c,d,e,f,g,h,i,j,k){});
 // CHECK-NEXT: function (a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10) { [bytecode] }
-print(Map.toString());
-// CHECK-NEXT: function Map() { [native code] }
+
+// Reconfigured .length
+function foo(x) {}
+Object.defineProperty(foo, "length", { value: 5 })
+print(foo);
+// CHECK-NEXT: function foo(a0, a1, a2, a3, a4) { [bytecode] }
 
 // Non-string .length
 var foo = function badlength(a, b, c){};
@@ -64,6 +68,12 @@ Object.defineProperty(foo, "length", {value:"aa"});
 print(foo);
 // CHECK-NEXT: function badlength() { [bytecode] }
 
+// NativeFunctions are printed as 0-arity.
+print(Map);
+// CHECK-NEXT: function Map() { [native code] }
+print(Math.pow);
+// CHECK-NEXT: function pow() { [native code] }
+
 print('call');
 // CHECK-LABEL: call
 var f = function(a, b) {