diff --git a/runtime/lib/ffi_dynamic_library.cc b/runtime/lib/ffi_dynamic_library.cc
index b083e04e390..68ec283019b 100644
--- a/runtime/lib/ffi_dynamic_library.cc
+++ b/runtime/lib/ffi_dynamic_library.cc
@@ -19,51 +19,14 @@
 
 namespace dart {
 
-// Concatenates a NULL terminated array of strings.
-// The returned string is scope allocated.
-// TODO(dacoharkes): Can we share this with runtime/bin/extensions.cc?
-const char* Concatenate(const char** strings) {
-  int size = 1;  // null termination.
-  for (int i = 0; strings[i] != NULL; i++) {
-    size += strlen(strings[i]);
-  }
-  char* result = reinterpret_cast<char*>(Dart_ScopeAllocate(size));
-  int index = 0;
-  for (int i = 0; strings[i] != NULL; i++) {
-    index += snprintf(result + index, size - index, "%s", strings[i]);
-  }
-  ASSERT(index == size - 1);
-  ASSERT(result[size - 1] == '\0');
-  return result;
-}
-
-// TODO(dacoharkes): Can we share this with runtime/bin/extensions.cc?
-const char* LibraryPath(const char* library_name) {
-  const char* library_prefix = "lib";
-#if defined(TARGET_OS_LINUX)
-  const char* library_extension = "so";
-#elif defined(TARGET_OS_MACOS)
-  const char* library_extension = "dylib";
-#else
-  const char* library_extension = "";
-  UNREACHABLE();
-#endif
-
-  const char* path_components[] = {
-      library_prefix, library_name, ".", library_extension, NULL,
-  };
-
-  return Concatenate(path_components);
-}
-
 DEFINE_NATIVE_ENTRY(Ffi_dl_open, 0, 1) {
 #if !defined(TARGET_OS_LINUX) && !defined(TARGET_OS_MACOS)
   UNREACHABLE();
 #else
-  GET_NON_NULL_NATIVE_ARGUMENT(String, argName, arguments->NativeArgAt(0));
+  GET_NON_NULL_NATIVE_ARGUMENT(String, lib_path, arguments->NativeArgAt(0));
 
   dlerror();  // Clear any errors.
-  void* handle = dlopen(LibraryPath(argName.ToCString()), RTLD_LAZY);
+  void* handle = dlopen(lib_path.ToCString(), RTLD_LAZY);
   if (handle == nullptr) {
     char* error = dlerror();
     const String& msg = String::Handle(
diff --git a/samples/ffi/dylib_utils.dart b/samples/ffi/dylib_utils.dart
new file mode 100644
index 00000000000..1929961e35f
--- /dev/null
+++ b/samples/ffi/dylib_utils.dart
@@ -0,0 +1,18 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:ffi' as ffi;
+import 'dart:io' show Platform;
+
+String _platformPath(String name, {String path}) {
+  if (path == null) path = "";
+  if (Platform.isLinux) return path + "lib" + name + ".so";
+  if (Platform.isMacOS) return path + "lib" + name + ".dylib";
+  throw Exception("Platform not implemented");
+}
+
+ffi.DynamicLibrary dlopenPlatformSpecific(String name, {String path}) {
+  String fullPath = _platformPath(name, path: path);
+  return ffi.DynamicLibrary.open(fullPath);
+}
diff --git a/samples/ffi/sample_ffi_dynamic_library.dart b/samples/ffi/sample_ffi_dynamic_library.dart
index cf834005a2d..234e3d020ab 100644
--- a/samples/ffi/sample_ffi_dynamic_library.dart
+++ b/samples/ffi/sample_ffi_dynamic_library.dart
@@ -4,12 +4,14 @@
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 typedef NativeDoubleUnOp = ffi.Double Function(ffi.Double);
 
 typedef DoubleUnOp = double Function(double);
 
 main(List<String> arguments) {
-  ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
   print(l);
   print(l.runtimeType);
 
diff --git a/samples/ffi/sample_ffi_functions.dart b/samples/ffi/sample_ffi_functions.dart
index 62b5718520d..4a3cf984a67 100644
--- a/samples/ffi/sample_ffi_functions.dart
+++ b/samples/ffi/sample_ffi_functions.dart
@@ -4,6 +4,8 @@
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 typedef NativeUnaryOp = ffi.Int32 Function(ffi.Int32);
 typedef NativeBinaryOp = ffi.Int32 Function(ffi.Int32, ffi.Int32);
 typedef UnaryOp = int Function(int);
@@ -93,7 +95,7 @@ main(List<String> arguments) {
   print('start main');
 
   ffi.DynamicLibrary ffiTestFunctions =
-      ffi.DynamicLibrary.open("ffi_test_functions");
+      dlopenPlatformSpecific("ffi_test_functions");
 
   {
     // int32 bin op
diff --git a/samples/ffi/sample_ffi_functions_callbacks.dart b/samples/ffi/sample_ffi_functions_callbacks.dart
index ddd68405f5e..8549377b064 100644
--- a/samples/ffi/sample_ffi_functions_callbacks.dart
+++ b/samples/ffi/sample_ffi_functions_callbacks.dart
@@ -4,6 +4,8 @@
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 import 'coordinate.dart';
 
 typedef NativeCoordinateOp = Coordinate Function(Coordinate);
@@ -33,7 +35,7 @@ main(List<String> arguments) {
   print('start main');
 
   ffi.DynamicLibrary ffiTestFunctions =
-      ffi.DynamicLibrary.open("ffi_test_functions");
+      dlopenPlatformSpecific("ffi_test_functions");
 
   {
     // pass a c pointer to a c function as an argument to a c function
diff --git a/samples/ffi/sample_ffi_functions_structs.dart b/samples/ffi/sample_ffi_functions_structs.dart
index ba076e007f2..d2b1e410a35 100644
--- a/samples/ffi/sample_ffi_functions_structs.dart
+++ b/samples/ffi/sample_ffi_functions_structs.dart
@@ -4,6 +4,8 @@
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 import 'coordinate.dart';
 
 typedef NativeCoordinateOp = Coordinate Function(Coordinate);
@@ -12,7 +14,7 @@ main(List<String> arguments) {
   print('start main');
 
   ffi.DynamicLibrary ffiTestFunctions =
-      ffi.DynamicLibrary.open("ffi_test_functions");
+      dlopenPlatformSpecific("ffi_test_functions");
 
   {
     // pass a struct to a c function and get a struct as return value
diff --git a/tests/standalone_2/ffi/dylib_utils.dart b/tests/standalone_2/ffi/dylib_utils.dart
new file mode 100644
index 00000000000..1929961e35f
--- /dev/null
+++ b/tests/standalone_2/ffi/dylib_utils.dart
@@ -0,0 +1,18 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:ffi' as ffi;
+import 'dart:io' show Platform;
+
+String _platformPath(String name, {String path}) {
+  if (path == null) path = "";
+  if (Platform.isLinux) return path + "lib" + name + ".so";
+  if (Platform.isMacOS) return path + "lib" + name + ".dylib";
+  throw Exception("Platform not implemented");
+}
+
+ffi.DynamicLibrary dlopenPlatformSpecific(String name, {String path}) {
+  String fullPath = _platformPath(name, path: path);
+  return ffi.DynamicLibrary.open(fullPath);
+}
diff --git a/tests/standalone_2/ffi/dynamic_library_test.dart b/tests/standalone_2/ffi/dynamic_library_test.dart
index 1c3c45dd578..0a38e9ad0bf 100644
--- a/tests/standalone_2/ffi/dynamic_library_test.dart
+++ b/tests/standalone_2/ffi/dynamic_library_test.dart
@@ -8,6 +8,8 @@ library FfiTest;
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 import 'package:expect/expect.dart';
 
 void main() {
@@ -20,13 +22,13 @@ void main() {
 }
 
 void testOpen() {
-  ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
   Expect.notEquals(null, l);
 }
 
 void testOpenError() {
   Expect.throws(
-      () => ffi.DynamicLibrary.open("doesnotexistforsurelibrary123409876"));
+      () => dlopenPlatformSpecific("doesnotexistforsurelibrary123409876"));
 }
 
 typedef NativeDoubleUnOp = ffi.Double Function(ffi.Double);
@@ -34,30 +36,30 @@ typedef NativeDoubleUnOp = ffi.Double Function(ffi.Double);
 typedef DoubleUnOp = double Function(double);
 
 void testLookup() {
-  ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
   var timesFour = l.lookupFunction<NativeDoubleUnOp, DoubleUnOp>("timesFour");
   Expect.approxEquals(12.0, timesFour(3));
 }
 
 void testLookupError() {
-  ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
   Expect.throws(() => l.lookupFunction<NativeDoubleUnOp, DoubleUnOp>(
       "functionnamethatdoesnotexistforsure749237593845"));
 }
 
 void testToString() {
-  ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
   Expect.stringEquals(
       "DynamicLibrary: handle=0x", l.toString().substring(0, 25));
 }
 
 void testEquality() {
-  ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
-  ffi.DynamicLibrary l2 = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l2 = dlopenPlatformSpecific("ffi_test_dynamic_library");
   Expect.equals(l, l2);
   Expect.equals(l.hashCode, l2.hashCode);
   Expect.notEquals(l, null);
   Expect.notEquals(null, l);
-  ffi.DynamicLibrary l3 = ffi.DynamicLibrary.open("ffi_test_functions");
+  ffi.DynamicLibrary l3 = dlopenPlatformSpecific("ffi_test_functions");
   Expect.notEquals(l, l3);
 }
diff --git a/tests/standalone_2/ffi/function_callbacks_test.dart b/tests/standalone_2/ffi/function_callbacks_test.dart
index 2f3212b8da1..98171829b47 100644
--- a/tests/standalone_2/ffi/function_callbacks_test.dart
+++ b/tests/standalone_2/ffi/function_callbacks_test.dart
@@ -8,6 +8,8 @@ library FfiTest;
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 import "package:expect/expect.dart";
 
 import 'coordinate.dart';
@@ -24,7 +26,7 @@ void main() {
 }
 
 ffi.DynamicLibrary ffiTestFunctions =
-    ffi.DynamicLibrary.open("ffi_test_functions");
+    dlopenPlatformSpecific("ffi_test_functions");
 
 /// pass a pointer to a c function as an argument to a c function
 void testFunctionWithFunctionPointer() {
diff --git a/tests/standalone_2/ffi/function_structs_test.dart b/tests/standalone_2/ffi/function_structs_test.dart
index 6f74a90bbd4..ce7bd1186cb 100644
--- a/tests/standalone_2/ffi/function_structs_test.dart
+++ b/tests/standalone_2/ffi/function_structs_test.dart
@@ -9,6 +9,8 @@ library FfiTest;
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 import "package:expect/expect.dart";
 
 import 'coordinate.dart';
@@ -23,7 +25,7 @@ void main() {
 }
 
 ffi.DynamicLibrary ffiTestFunctions =
-    ffi.DynamicLibrary.open("ffi_test_functions");
+    dlopenPlatformSpecific("ffi_test_functions");
 
 /// pass a struct to a c function and get a struct as return value
 void testFunctionWithStruct() {
diff --git a/tests/standalone_2/ffi/function_test.dart b/tests/standalone_2/ffi/function_test.dart
index bed0264b025..dacce5ddf3e 100644
--- a/tests/standalone_2/ffi/function_test.dart
+++ b/tests/standalone_2/ffi/function_test.dart
@@ -8,6 +8,8 @@ library FfiTest;
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 import "package:expect/expect.dart";
 
 void main() {
@@ -29,7 +31,7 @@ void main() {
 }
 
 ffi.DynamicLibrary ffiTestFunctions =
-    ffi.DynamicLibrary.open("ffi_test_functions");
+    dlopenPlatformSpecific("ffi_test_functions");
 
 typedef NativeBinaryOp = ffi.Int32 Function(ffi.Int32, ffi.Int32);
 typedef UnaryOp = int Function(int);
diff --git a/tests/standalone_2/ffi/static_checks_test.dart b/tests/standalone_2/ffi/static_checks_test.dart
index 422fc6f97a6..15e162a97b0 100644
--- a/tests/standalone_2/ffi/static_checks_test.dart
+++ b/tests/standalone_2/ffi/static_checks_test.dart
@@ -8,6 +8,8 @@ library FfiTest;
 
 import 'dart:ffi' as ffi;
 
+import 'dylib_utils.dart';
+
 void main() {
   testGetGeneric();
   testGetGeneric2();
@@ -245,7 +247,7 @@ void testFromFunctionTearOff() {
 
 void testLookupFunctionGeneric() {
   Function generic<T extends Function>() {
-    ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+    ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
     Function result;
     result = l.lookupFunction<T, DoubleUnOp>("cos"); //# 15: compile-time error
     return result;
@@ -256,7 +258,7 @@ void testLookupFunctionGeneric() {
 
 void testLookupFunctionGeneric2() {
   Function generic<T extends Function>() {
-    ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+    ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
     Function result;
     result = //# 16: compile-time error
         l.lookupFunction<NativeDoubleUnOp, T>("cos"); //# 16: compile-time error
@@ -267,12 +269,12 @@ void testLookupFunctionGeneric2() {
 }
 
 void testLookupFunctionWrongNativeFunctionSignature() {
-  ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
   l.lookupFunction<IntUnOp, IntUnOp>("cos"); //# 17: compile-time error
 }
 
 void testLookupFunctionTypeMismatch() {
-  ffi.DynamicLibrary l = ffi.DynamicLibrary.open("ffi_test_dynamic_library");
+  ffi.DynamicLibrary l = dlopenPlatformSpecific("ffi_test_dynamic_library");
   l.lookupFunction<NativeDoubleUnOp, IntUnOp>("cos"); //# 18: compile-time error
 }