diff --git a/spec/std/atomic_spec.cr b/spec/std/atomic_spec.cr
index 2b0d6d18746a..ea08a33ea914 100644
--- a/spec/std/atomic_spec.cr
+++ b/spec/std/atomic_spec.cr
@@ -1,130 +1,129 @@
-# TODO: enable after 0.19.3
-# require "spec"
-
-# describe Atomic do
-#   it "compares and sets with integer" do
-#     atomic = Atomic.new(1)
-
-#     atomic.compare_and_set(2, 3).should eq({1, false})
-#     atomic.get.should eq(1)
-
-#     atomic.compare_and_set(1, 3).should eq({1, true})
-#     atomic.get.should eq(3)
-#   end
-
-#   it "compares and sets with nilable type" do
-#     atomic = Atomic(String?).new(nil)
-#     string = "hello"
-
-#     atomic.compare_and_set(string, "foo").should eq({nil, false})
-#     atomic.get.should be_nil
-
-#     atomic.compare_and_set(nil, string).should eq({nil, true})
-#     atomic.get.should be(string)
-
-#     atomic.compare_and_set(string, nil).should eq({string, true})
-#     atomic.get.should be_nil
-#   end
-
-#   it "compares and sets with reference type" do
-#     str1 = "hello"
-#     str2 = "bye"
-
-#     atomic = Atomic(String).new(str1)
-
-#     atomic.compare_and_set(str2, "foo").should eq({str1, false})
-#     atomic.get.should eq(str1)
-
-#     atomic.compare_and_set(str1, str2).should eq({str1, true})
-#     atomic.get.should be(str2)
-
-#     atomic.compare_and_set(str2, str1).should eq({str2, true})
-#     atomic.get.should be(str1)
-#   end
-
-#   it "#adds" do
-#     atomic = Atomic.new(1)
-#     atomic.add(2).should eq(1)
-#     atomic.get.should eq(3)
-#   end
-
-#   it "#sub" do
-#     atomic = Atomic.new(1)
-#     atomic.sub(2).should eq(1)
-#     atomic.get.should eq(-1)
-#   end
-
-#   it "#and" do
-#     atomic = Atomic.new(5)
-#     atomic.and(3).should eq(5)
-#     atomic.get.should eq(1)
-#   end
-
-#   it "#nand" do
-#     atomic = Atomic.new(5)
-#     atomic.nand(3).should eq(5)
-#     atomic.get.should eq(-2)
-#   end
-
-#   it "#or" do
-#     atomic = Atomic.new(5)
-#     atomic.or(2).should eq(5)
-#     atomic.get.should eq(7)
-#   end
-
-#   it "#xor" do
-#     atomic = Atomic.new(5)
-#     atomic.xor(3).should eq(5)
-#     atomic.get.should eq(6)
-#   end
-
-#   it "#max with signed" do
-#     atomic = Atomic.new(5)
-#     atomic.max(2).should eq(5)
-#     atomic.get.should eq(5)
-#     atomic.max(10).should eq(5)
-#     atomic.get.should eq(10)
-#   end
-
-#   it "#max with unsigned" do
-#     atomic = Atomic.new(5_u32)
-#     atomic.max(2_u32).should eq(5_u32)
-#     atomic.get.should eq(5_u32)
-#     atomic.max(UInt32::MAX).should eq(5_u32)
-#     atomic.get.should eq(UInt32::MAX)
-#   end
-
-#   it "#min with signed" do
-#     atomic = Atomic.new(5)
-#     atomic.min(10).should eq(5)
-#     atomic.get.should eq(5)
-#     atomic.min(2).should eq(5)
-#     atomic.get.should eq(2)
-#   end
-
-#   it "#min with unsigned" do
-#     atomic = Atomic.new(UInt32::MAX)
-#     atomic.min(10_u32).should eq(UInt32::MAX)
-#     atomic.get.should eq(10_u32)
-#     atomic.min(15_u32).should eq(10_u32)
-#     atomic.get.should eq(10_u32)
-#   end
-
-#   it "#set" do
-#     atomic = Atomic.new(1)
-#     atomic.set(2).should eq(2)
-#     atomic.get.should eq(2)
-#   end
-
-#   it "#lazy_set" do
-#     atomic = Atomic.new(1)
-#     atomic.lazy_set(2).should eq(2)
-#     atomic.get.should eq(2)
-#   end
-
-#   it "#swap" do
-#     atomic = Atomic.new(1)
-#     atomic.swap(2).should eq(1)
-#     atomic.get.should eq(2)
-#   end
-# end
+require "spec"
+
+describe Atomic do
+  it "compares and sets with integer" do
+    atomic = Atomic.new(1)
+
+    atomic.compare_and_set(2, 3).should eq({1, false})
+    atomic.get.should eq(1)
+
+    atomic.compare_and_set(1, 3).should eq({1, true})
+    atomic.get.should eq(3)
+  end
+
+  it "compares and sets with nilable type" do
+    atomic = Atomic(String?).new(nil)
+    string = "hello"
+
+    atomic.compare_and_set(string, "foo").should eq({nil, false})
+    atomic.get.should be_nil
+
+    atomic.compare_and_set(nil, string).should eq({nil, true})
+    atomic.get.should be(string)
+
+    atomic.compare_and_set(string, nil).should eq({string, true})
+    atomic.get.should be_nil
+  end
+
+  it "compares and sets with reference type" do
+    str1 = "hello"
+    str2 = "bye"
+
+    atomic = Atomic(String).new(str1)
+
+    atomic.compare_and_set(str2, "foo").should eq({str1, false})
+    atomic.get.should eq(str1)
+
+    atomic.compare_and_set(str1, str2).should eq({str1, true})
+    atomic.get.should be(str2)
+
+    atomic.compare_and_set(str2, str1).should eq({str2, true})
+    atomic.get.should be(str1)
+  end
+
+  it "#adds" do
+    atomic = Atomic.new(1)
+    atomic.add(2).should eq(1)
+    atomic.get.should eq(3)
+  end
+
+  it "#sub" do
+    atomic = Atomic.new(1)
+    atomic.sub(2).should eq(1)
+    atomic.get.should eq(-1)
+  end
+
+  it "#and" do
+    atomic = Atomic.new(5)
+    atomic.and(3).should eq(5)
+    atomic.get.should eq(1)
+  end
+
+  it "#nand" do
+    atomic = Atomic.new(5)
+    atomic.nand(3).should eq(5)
+    atomic.get.should eq(-2)
+  end
+
+  it "#or" do
+    atomic = Atomic.new(5)
+    atomic.or(2).should eq(5)
+    atomic.get.should eq(7)
+  end
+
+  it "#xor" do
+    atomic = Atomic.new(5)
+    atomic.xor(3).should eq(5)
+    atomic.get.should eq(6)
+  end
+
+  it "#max with signed" do
+    atomic = Atomic.new(5)
+    atomic.max(2).should eq(5)
+    atomic.get.should eq(5)
+    atomic.max(10).should eq(5)
+    atomic.get.should eq(10)
+  end
+
+  it "#max with unsigned" do
+    atomic = Atomic.new(5_u32)
+    atomic.max(2_u32).should eq(5_u32)
+    atomic.get.should eq(5_u32)
+    atomic.max(UInt32::MAX).should eq(5_u32)
+    atomic.get.should eq(UInt32::MAX)
+  end
+
+  it "#min with signed" do
+    atomic = Atomic.new(5)
+    atomic.min(10).should eq(5)
+    atomic.get.should eq(5)
+    atomic.min(2).should eq(5)
+    atomic.get.should eq(2)
+  end
+
+  it "#min with unsigned" do
+    atomic = Atomic.new(UInt32::MAX)
+    atomic.min(10_u32).should eq(UInt32::MAX)
+    atomic.get.should eq(10_u32)
+    atomic.min(15_u32).should eq(10_u32)
+    atomic.get.should eq(10_u32)
+  end
+
+  it "#set" do
+    atomic = Atomic.new(1)
+    atomic.set(2).should eq(2)
+    atomic.get.should eq(2)
+  end
+
+  it "#lazy_set" do
+    atomic = Atomic.new(1)
+    atomic.lazy_set(2).should eq(2)
+    atomic.get.should eq(2)
+  end
+
+  it "#swap" do
+    atomic = Atomic.new(1)
+    atomic.swap(2).should eq(1)
+    atomic.get.should eq(2)
+  end
+end