diff --git a/package.json b/package.json
index e073c59..1db8f61 100644
--- a/package.json
+++ b/package.json
@@ -9,7 +9,7 @@
   },
   "scripts": {
     "test": "npm run generate && mocha test --recursive",
-    "test:dev": "npm run generate && mocha ./test/parse",
+    "test:dev": "npm run generate && mocha ./test/syntax",
     "test:cov": "nyc --reporter=lcov npm run test",
     "test:bin": "npm run generate && node bin/heta.js run test/parse/input/include.heta",
     "generate": "pegjs -o src/index.js src/pegjs/heta.pegjs"
diff --git a/src/index.js b/src/index.js
index 6eca734..00a9975 100644
--- a/src/index.js
+++ b/src/index.js
@@ -290,13 +290,23 @@ function peg$parse(input, options) {
       peg$c71 = /^[^;{#@']/,
       peg$c72 = peg$classExpectation([";", "{", "#", "@", "'"], true, false),
       peg$c73 = function(s) {
-          let str = s.join('').replace(/[\s]+/g, ' ').replace(/^ +/g, '').replace(/ +$/g, '');
+          let str = s.join('')
+            .replace(/[\s]+/g, ' ') // remove multiple spaces
+            .replace(/^ +/g, '')    // remove leading spaces
+            .replace(/ +$/g, '');   // remove trailing spaces
           let doubleRegExpr = /^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$/;
-          let res = doubleRegExpr.test(str)
-              ? parseFloat(str)
-              : str;
-
-          return res;
+          
+          if (str === 'null') {
+            return null;
+          } else if (str === 'true') {
+            return true;
+          } else if (str === 'false') {
+            return false;
+          } else if (doubleRegExpr.test(str)) {
+            return parseFloat(str);
+          } else {
+            return str;
+          }
         },
       peg$c74 = peg$otherExpectation("Include"),
       peg$c75 = "include",
@@ -372,7 +382,9 @@ function peg$parse(input, options) {
           // XXX: alternative but bad solution, remove trailing comments
           //let str = s.match(/\s*(.*?)\s*(?:\/\/|\/\*|$)/)[1] // ignores text after // or /*
 
-          if (str === 'true') {
+          if (str === 'null') {
+            res = null;
+          } else if (str === 'true') {
             var res = true
           } else if (str === 'false') {
             res = false
diff --git a/src/pegjs/heta.pegjs b/src/pegjs/heta.pegjs
index 8796b1a..0ed22b7 100644
--- a/src/pegjs/heta.pegjs
+++ b/src/pegjs/heta.pegjs
@@ -131,13 +131,23 @@ QuotedString "Quoted String"= (Break/Space)* "\"" s: [^"]* "\""
 // all string until stop list, trim spaces
 AssignString "Assignment String" = s: [^;{#@']*
   {
-    let str = s.join('').replace(/[\s]+/g, ' ').replace(/^ +/g, '').replace(/ +$/g, '');
+    let str = s.join('')
+      .replace(/[\s]+/g, ' ') // remove multiple spaces
+      .replace(/^ +/g, '')    // remove leading spaces
+      .replace(/ +$/g, '');   // remove trailing spaces
     let doubleRegExpr = /^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$/;
-    let res = doubleRegExpr.test(str)
-        ? parseFloat(str)
-        : str;
-
-    return res;
+    
+    if (str === 'null') {
+      return null;
+    } else if (str === 'true') {
+      return true;
+    } else if (str === 'false') {
+      return false;
+    } else if (doubleRegExpr.test(str)) {
+      return parseFloat(str);
+    } else {
+      return str;
+    }
   }
 
 // -- BLOCKS --
@@ -221,7 +231,9 @@ String "String" = (Break/Space)* s: $([^,[\]{};] !"//" !"/*")+ Comment?
     // XXX: alternative but bad solution, remove trailing comments
     //let str = s.match(/\s*(.*?)\s*(?:\/\/|\/\*|$)/)[1] // ignores text after // or /*
 
-    if (str === 'true') {
+    if (str === 'null') {
+      res = null;
+    } else if (str === 'true') {
       var res = true
     } else if (str === 'false') {
       res = false
diff --git a/test/parse/index.js b/test/parse/index.js
index 72b9300..d764d4e 100644
--- a/test/parse/index.js
+++ b/test/parse/index.js
@@ -21,6 +21,7 @@ const cases = [
   { source: './input/other-tabs.heta', target: './output/other-tabs.json' },
   { source: './input/other-strings.heta', target: './output/other-strings.json' },
   { source: './input/empty-statement.heta', target: './output/empty-statement.json' },
+  { source: './input/null.heta', target: './output/null.json' },
 ];
 
 describe('Check "parse"', () => {
diff --git a/test/parse/input/null.heta b/test/parse/input/null.heta
new file mode 100644
index 0000000..136d939
--- /dev/null
+++ b/test/parse/input/null.heta
@@ -0,0 +1,4 @@
+x1 @Record := 5;
+x1 := null;
+
+x2 @Record {assignments: {start_: null}};
diff --git a/test/parse/output/null.json b/test/parse/output/null.json
new file mode 100644
index 0000000..07de37d
--- /dev/null
+++ b/test/parse/output/null.json
@@ -0,0 +1,5 @@
+[
+    { "action": "upsert", "id": "x1", "class": "Record", "assignments": {"ode_": 5}},
+    { "action": "upsert", "id": "x1", "assignments": {"ode_": null}},
+    { "action": "upsert", "id": "x2", "class": "Record", "assignments": {"start_": null}}
+]
\ No newline at end of file
diff --git a/test/syntax/index.js b/test/syntax/index.js
index f581699..cbd8b81 100644
--- a/test/syntax/index.js
+++ b/test/syntax/index.js
@@ -437,6 +437,52 @@ let to_test = [
       id: 'p1',
       string: 'xxx/yyy'
     }]
+  },
+  // null
+  {
+    description: 'null as property',
+    source: 'p1 {key: null};',
+    expectation: [{
+      action: 'upsert',
+      id: 'p1',
+      key: null
+    }]
+  },
+  {
+    description: 'null as deep property',
+    source: 'p1 {key: {subkey: null}};',
+    expectation: [{
+      action: 'upsert',
+      id: 'p1',
+      key: {subkey: null}
+    }]
+  },
+  {
+    description: 'null as array element',
+    source: 'p1 {key: [null]};',
+    expectation: [{
+      action: 'upsert',
+      id: 'p1',
+      key: [null]
+    }]
+  },
+  {
+    description: 'null inside assignment',
+    source: 'p1 .= null;',
+    expectation: [{
+      action: 'upsert',
+      id: 'p1',
+      assignments: {start_: null}
+    }]
+  },
+  {
+    description: 'null inside assignment expression',
+    source: 'p1 .= a + null;',
+    expectation: [{
+      action: 'upsert',
+      id: 'p1',
+      assignments: {start_: 'a + null'}
+    }]
   }
 ];