diff --git a/krakenGrammer.kgm b/krakenGrammer.kgm
index 4f0157e..2a12825 100644
--- a/krakenGrammer.kgm
+++ b/krakenGrammer.kgm
@@ -83,9 +83,8 @@ opt_parameter_list = parameter_list | ;
 parameter_list = parameter_list WS "," WS parameter | parameter ;
 parameter = boolean_expression ;
 
-def_nonterm = "def" ;
-obj_nonterm = "obj" ;
-type_def = def_nonterm WS identifier WS type | obj_nonterm WS identifier WS template_dec WS "{" WS declaration_block WS "}" | obj_nonterm WS identifier WS "{" WS declaration_block WS "}" | obj_nonterm WS identifier WS template_dec WS traits WS "{" WS declaration_block WS "}" | obj_nonterm WS identifier WS traits WS "{" WS declaration_block WS "}" ;
+obj_nonterm = "obj" | "uni" ;
+type_def = obj_nonterm WS identifier WS template_dec WS "{" WS declaration_block WS "}" | obj_nonterm WS identifier WS "{" WS declaration_block WS "}" | obj_nonterm WS identifier WS template_dec WS traits WS "{" WS declaration_block WS "}" | obj_nonterm WS identifier WS traits WS "{" WS declaration_block WS "}" ;
 
 declaration_block = declaration_statement line_end WS declaration_block | function WS declaration_block | declaration_statement line_end | function | ;
 traits = "\(" WS trait_list WS "\)" ;
diff --git a/stdlib/ast_nodes.krak b/stdlib/ast_nodes.krak
index e466ea7..1945db3 100644
--- a/stdlib/ast_nodes.krak
+++ b/stdlib/ast_nodes.krak
@@ -190,8 +190,10 @@ obj identifier (Object) {
         return name == other.name && type == other.type && enclosing_scope == other.enclosing_scope
     }
 }
-fun ast_type_def_ptr(name: string): *ast_node {
-    var to_ret.construct(name): type_def
+fun ast_type_def_ptr(name: ref string): *ast_node
+    return ast_type_def_ptr(name, false)
+fun ast_type_def_ptr(name: ref string, is_union: bool): *ast_node {
+    var to_ret.construct(name, is_union): type_def
     var ptr = new<ast_node>()
     ptr->copy_construct(&ast_node::type_def(to_ret))
     return ptr
@@ -205,12 +207,14 @@ fun is_type_def(node: *ast_node): bool {
 obj type_def (Object) {
     var scope: map<string, vector<*ast_node>>
     var name: string
+    var is_union: bool
     var self_type: *type
     var variables: vector<*ast_node>
     var methods: vector<*ast_node>
-    fun construct(nameIn: string): *type_def  {
+    fun construct(nameIn: ref string, is_unionIn: bool): *type_def  {
         scope.construct()
         name.copy_construct(&nameIn)
+        is_union = is_unionIn
         self_type = null<type>()
         variables.construct()
         methods.construct()
@@ -220,6 +224,7 @@ obj type_def (Object) {
         self_type = old->self_type
         scope.copy_construct(&old->scope)
         name.copy_construct(&old->name)
+        is_union = old->is_union
         variables.copy_construct(&old->variables)
         methods.copy_construct(&old->methods)
     }
@@ -234,7 +239,7 @@ obj type_def (Object) {
         copy_construct(&other)
     }
     fun operator==(other: ref type_def): bool {
-        return name == other.name && self_type == other.self_type && variables == other.variables && methods == other.methods
+        return name == other.name && is_union == other.is_union && self_type == other.self_type && variables == other.variables && methods == other.methods
     }
 }
 fun ast_adt_def_ptr(name: string): *ast_node {
@@ -1128,7 +1133,7 @@ fun get_ast_name(node: *ast_node): string {
         ast_node::translation_unit(backing) return string("translation_unit: ") + backing.name
         ast_node::import(backing) return string("import: ") + backing.name + "; [" + backing.imported.reduce(fun(name: string, acc: string): string return acc + " " + name;, string()) + " ]"
         ast_node::identifier(backing) return string("identifier: ") + backing.name + ": " + backing.type->to_string()
-        ast_node::type_def(backing) return string("type_def: ") + backing.name
+        ast_node::type_def(backing) return string("type_def: ") + backing.name + " union?:" + backing.is_union
         ast_node::adt_def(backing) return string("adt_def: ") + backing.name
         ast_node::function(backing) {
             if (backing.is_extern)
diff --git a/stdlib/ast_transformation.krak b/stdlib/ast_transformation.krak
index 01fd189..8dac84e 100644
--- a/stdlib/ast_transformation.krak
+++ b/stdlib/ast_transformation.krak
@@ -103,7 +103,8 @@ obj ast_transformation (Object) {
             add_to_scope(name, template, scope)
             return template
         } else {
-            var type_def_node = ast_type_def_ptr(name)
+            // pass in whether or not this is a union
+            var type_def_node = ast_type_def_ptr(name, concat_symbol_tree(get_node("obj_nonterm", child)) == "uni")
             type_def_node->type_def.self_type = type_ptr(type_def_node, transform_traits(get_node("traits", child)))
             ast_to_syntax.set(type_def_node, child)
             add_to_scope("~enclosing_scope", scope, type_def_node)
diff --git a/stdlib/c_generator.krak b/stdlib/c_generator.krak
index d2032b3..9db2783 100644
--- a/stdlib/c_generator.krak
+++ b/stdlib/c_generator.krak
@@ -445,8 +445,16 @@ obj c_generator (Object) {
         type_poset.get_sorted().for_each(fun(vert: *ast_node) {
             /*var base_name = vert->type_def.name*/
             var base_name = get_name(vert)
-            plain_typedefs += string("typedef struct ") + base_name + "_dummy " + base_name + ";\n"
-            structs += string("struct ") + base_name + "_dummy {\n"
+            plain_typedefs += string("typedef ")
+            if (vert->type_def.is_union) {
+                plain_typedefs += "union "
+                structs += "union "
+            } else {
+                plain_typedefs += "struct "
+                structs += "struct "
+            }
+            plain_typedefs += base_name + "_dummy " + base_name + ";\n"
+            structs += base_name + "_dummy {\n"
             if (is_type_def(vert)) {
                 vert->type_def.variables.for_each(fun(variable_declaration: *ast_node) structs += generate_declaration_statement(variable_declaration, null<ast_node>(), null<ast_node>(), null<stack<pair<bool,stack<*ast_node>>>>(), false).one_string() + ";\n";) // also no defer stack
                 // generate the methods (note some of these may be templates)
diff --git a/stdlib/importer.krak b/stdlib/importer.krak
index 5c0ad88..b339f97 100644
--- a/stdlib/importer.krak
+++ b/stdlib/importer.krak
@@ -123,8 +123,7 @@ obj importer (Object) {
         remove_node(symbol("\"while\"", true), parse_tree)
         remove_node(symbol("\"__if_comp__\"", true), parse_tree)
         remove_node(symbol("\"comp_simple_passthrough\"", true), parse_tree)
-        remove_node(symbol("def_nonterm", false), parse_tree)
-        remove_node(symbol("obj_nonterm", false), parse_tree)
+        /*remove_node(symbol("obj_nonterm", false), parse_tree)*/
         remove_node(symbol("adt_nonterm", false), parse_tree)
 
         collapse_node(symbol("case_statement_list", false), parse_tree)
diff --git a/stdlib/string.krak b/stdlib/string.krak
index 3126e00..db1b1ae 100644
--- a/stdlib/string.krak
+++ b/stdlib/string.krak
@@ -4,6 +4,9 @@ import mem
 import serialize
 import io
 
+fun to_string(in: bool): string
+    if (in) return string("true")
+    else return string("false")
 fun to_string(in: uchar): string
     return to_string_num(in)
 fun to_string(in: short): string
@@ -168,6 +171,7 @@ obj string (Object, Serializable) {
     }
 
     fun operator+(integer: int): string return *this + to_string(integer);
+    fun operator+(b: bool): string return *this + to_string(b);
 
     fun operator+(str: *char): string {
         var newStr.construct(str):string
@@ -181,6 +185,7 @@ obj string (Object, Serializable) {
     }
 
     fun operator+=(integer: int) *this += to_string(integer);
+    fun operator+=(b: bool) *this += to_string(b);
 
     fun operator+=(character: char): void {
         data += character
diff --git a/tests/test_union.expected_results b/tests/test_union.expected_results
new file mode 100644
index 0000000..c88bae3
--- /dev/null
+++ b/tests/test_union.expected_results
@@ -0,0 +1,3 @@
+true
+4
+4.400000
diff --git a/tests/test_union.krak b/tests/test_union.krak
new file mode 100644
index 0000000..4397307
--- /dev/null
+++ b/tests/test_union.krak
@@ -0,0 +1,22 @@
+import io:*
+
+uni packed {
+    var a: int
+    var b: double
+}
+
+obj loose {
+    var a: int
+    var b: double
+}
+
+fun main():int {
+    var a: packed
+    var b: loose
+    println(#sizeof<packed> < #sizeof<loose>)
+    a.a = 4
+    println(a.a)
+    a.b = 4.4
+    println(a.b)
+    return 0
+}