diff --git a/spec/std/json/serialization_spec.cr b/spec/std/json/serialization_spec.cr
index 249a727b77c6..c61cee52c3ca 100644
--- a/spec/std/json/serialization_spec.cr
+++ b/spec/std/json/serialization_spec.cr
@@ -120,11 +120,11 @@ describe "JSON serialization" do
       Union(Bool, Array(Int32)).from_json(%(true)).should be_true
     end
 
-    {% for type in %w(Int8 Int16 Int32 Int64 UInt8 UInt16 UInt32 UInt64).map(&.id) %}
-        it "deserializes union with {{type}} (fast path)" do
-          Union({{type}}, Array(Int32)).from_json(%(#{ {{type}}::MAX })).should eq({{type}}::MAX)
-        end
-      {% end %}
+    {% for type in Int::Primitive.union_types %}
+      it "deserializes union with {{type}} (fast path)" do
+        Union({{type}}, Array(Int32)).from_json(%(#{ {{type}}::MAX })).should eq({{type}}::MAX)
+      end
+    {% end %}
 
     it "deserializes union with Float32 (fast path)" do
       Union(Float32, Array(Int32)).from_json(%(1)).should eq(1)
diff --git a/src/json/from_json.cr b/src/json/from_json.cr
index 56b396a5e80b..b7ed5ef5abc2 100644
--- a/src/json/from_json.cr
+++ b/src/json/from_json.cr
@@ -66,7 +66,7 @@ def Bool.new(pull : JSON::PullParser)
   pull.read_bool
 end
 
-{% for type in %w(Int8 Int16 Int32 Int64 UInt8 UInt16 UInt32 UInt64) %}
+{% for type in Int::Primitive.union_types %}
   def {{type.id}}.new(pull : JSON::PullParser)
     {{type.id}}.new(pull.read_int)
   end
diff --git a/src/random/system.cr b/src/random/system.cr
index 54fdbebfd440..a9ca0dae272f 100644
--- a/src/random/system.cr
+++ b/src/random/system.cr
@@ -18,7 +18,7 @@ module Random::System
     Crystal::System::Random.next_u
   end
 
-  {% for type in [UInt8, UInt16, UInt32, UInt64] %}
+  {% for type in Int::Unsigned.union_types %}
     # Generates a random integer of a given type. The number of bytes to
     # generate can be limited; by default it will generate as many bytes as
     # needed to fill the integer size.
@@ -46,7 +46,7 @@ module Random::System
     end
   {% end %}
 
-  {% for type in [Int8, Int16, Int32, Int64] %}
+  {% for type in Int::Signed.union_types %}
     private def rand_type(type : {{type}}.class, needed_bytes = sizeof({{type}})) : {{type}}
       result = rand_type({{"U#{type}".id}}, needed_bytes)
       {{type}}.new(result)
diff --git a/src/yaml/from_yaml.cr b/src/yaml/from_yaml.cr
index 62d293164805..5554756c7611 100644
--- a/src/yaml/from_yaml.cr
+++ b/src/yaml/from_yaml.cr
@@ -34,7 +34,7 @@ def Bool.new(pull : YAML::PullParser)
   pull.read_scalar == "true"
 end
 
-{% for type in %w(Int8 Int16 Int32 Int64 UInt8 UInt16 UInt32 UInt64) %}
+{% for type in Int::Primitive.union_types %}
   def {{type.id}}.new(pull : YAML::PullParser)
     location = pull.location
     begin