diff --git a/src/ReadWriteLocks.jl b/src/ReadWriteLocks.jl
index fbe7c28..b1d0868 100644
--- a/src/ReadWriteLocks.jl
+++ b/src/ReadWriteLocks.jl
@@ -17,16 +17,23 @@ struct WriteLock{T<:AbstractLock}
     rwlock::T
 end
 
-mutable struct ReadWriteLock <: AbstractLock
+# Need Julia VERSION > v"1.2.0-DEV.28` to have `ReentrantLock <: AbstractLock`
+LockTypes = Union{AbstractLock, ReentrantLock}
+mutable struct ReadWriteLock{L<:LockTypes} <: AbstractLock
     readers::Int
     writer::Bool
-    lock::ReentrantLock  # reentrant mutex
+    lock::L  # reentrant mutex
     condition::Condition
     read_lock::ReadLock
     write_lock::WriteLock
 
-    function ReadWriteLock()
-        rwlock = new(false, 0, ReentrantLock(), Condition())
+    function ReadWriteLock(
+        readers::Int=0,
+        writer::Bool=false,
+        lock::L=ReentrantLock(),
+        condition::Condition=Condition(),
+    ) where L <: LockTypes
+        rwlock = new{L}(readers, writer, lock, condition)
         rwlock.read_lock = ReadLock(rwlock)
         rwlock.write_lock = WriteLock(rwlock)
 
diff --git a/test/runtests.jl b/test/runtests.jl
index 131b899..89a27f6 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -3,6 +3,11 @@ using Test
 
 @testset "ReadWriteLock" begin
 
+@testset "Constructor" begin
+    @test ReadWriteLock() isa ReadWriteLock{ReentrantLock}
+    @test ReadWriteLock(0, false, Threads.Mutex()) isa ReadWriteLock{Threads.Mutex}
+end
+
 @testset "Single-threaded tests" begin
     @testset "Initialization" begin
         rwlock = ReadWriteLock()