yep

index.js

@@ -11,7 +11,8 @@ function assembler (input) {
         directive(),
         instruction(),
         label(),
-        mona.eol()
+        mona.eol(),
+        mona.eof()
       )
     ),
     input

parsers/instruction.js

@@ -24,16 +24,24 @@ function instructionName () {
 
 function instruction () {
   return mona.sequence((s) => {
-    const i = s(instructionName())
+    const i = s(
+      mona.followedBy(
+        instructionName(),
+        mona.maybe(mona.eol())
+      )
+    )
+
     const args = s(
       mona.maybe(
         mona.and(
           mona.spaces(),
-          parameters()
+          mona.followedBy(
+            parameters(),
+            mona.maybe(mona.eol())
+          )
         )
       )
     )
-    const nl = s(mona.eol())
     return mona.value({
       instruction: i,
       args: args

test/assembler.js

@@ -8,10 +8,9 @@ tap.test('should parse the basics', (t) => {
     {
       directive: '.org',
       args: [
-        [
-          'address',
-          'C000'
-        ]
+        {
+          'address': 'C000'
+        }
       ]
     },
     {

test/instruction.js

@@ -5,7 +5,7 @@ const instructionParser = require('../parsers/instruction')
 tap.test('will parse an instruction', (t) => {
   t.plan(1)
   t.deepEqual(mona.parse(instructionParser(), 'sei\n'), {
-    args: [],
+    args: null,
     instruction: 'sei'
   })
 })