diff --git a/src/grammar/brightscript.tmLanguage.spec.ts b/src/grammar/brightscript.tmLanguage.spec.ts
index 49612667..0924f43d 100644
--- a/src/grammar/brightscript.tmLanguage.spec.ts
+++ b/src/grammar/brightscript.tmLanguage.spec.ts
@@ -822,6 +822,60 @@ describe('brightscript.tmlanguage.json', () => {
         `);
     });
 
+    it(`handles standalone comment inside enum block`, async () => {
+        await testGrammar(`
+             enum DeviceContext
+            '     ^^^^^^^^^^^^^ entity.name.type.enum.brs
+            '^^^^ storage.type.enum.brs
+
+             ' This is a standalone comment
+            '^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line.apostrophe.brs
+
+             value = 1
+            '         ^ constant.numeric.brs
+            '       ^ keyword.operator.assignment.brs
+            '^^^^^ variable.object.enummember.brs
+
+             end enum
+            '^^^^^^^^ storage.type.enum.brs
+        `);
+    });
+
+    it('handles `end sub` preceded by a colon', async () => {
+        await testGrammar(`
+             if true then doSomething() : end sub
+            '                           ^^^^^^^^^ keyword.declaration.function.brs
+        `);
+
+        await testGrammar(`
+             if true then doSomething() : end function
+            '                           ^^^^^^^^^^^^^ keyword.declaration.function.brs
+        `);
+    });
+
+    it('handles optional keyword in interface fields', async () => {
+        await testGrammar(`
+            interface Person
+                optional name as string
+               '                 ^^^^^^ storage.type.brs
+               '              ^^ keyword.control.as.brs
+               '         ^^^^ variable.object.property.brs
+               '^^^^^^^^ storage.modifier.brs
+        `);
+    });
+
+    it('handles optional keyword in interface functions', async () => {
+        await testGrammar(`
+            interface Person
+                optional sub test() as string
+               '                      ^^^^^^ storage.type.brs
+               '                   ^^ keyword.control.as.brs
+               '             ^^^^ entity.name.function.member.brs
+               '         ^^^ storage.type.function.brs
+               '^^^^^^^^ storage.modifier.brs
+        `);
+    });
+
     it('handles named function declarations', async () => {
         await testGrammar(`
              sub write()
diff --git a/syntaxes/brightscript.tmLanguage.json b/syntaxes/brightscript.tmLanguage.json
index ea371cb1..712698f6 100644
--- a/syntaxes/brightscript.tmLanguage.json
+++ b/syntaxes/brightscript.tmLanguage.json
@@ -792,12 +792,15 @@
             }
         },
         "interface_field": {
-            "begin": "(?i)\\s*\\b([a-z0-9_]+)(?:[\\s\\t]*(as))?",
+            "begin": "(?i)\\s*\\b(?:(optional)[\\s\\t]+)?\\b([a-z0-9_]+)(?:[\\s\\t]*(as))?",
             "beginCaptures": {
                 "1": {
-                    "name": "variable.object.property.brs"
+                    "name": "storage.modifier.brs"
                 },
                 "2": {
+                    "name": "variable.object.property.brs"
+                },
+                "3": {
                     "name": "keyword.control.as.brs"
                 }
             },
@@ -822,41 +825,44 @@
             ]
         },
         "interface_function_plain": {
-            "match": "(?i:\\s*\\b(function|sub)[\\s\\t]+([a-z0-9_]+)(\\())(\\))[\\s\\t]",
+            "match": "(?i:\\s*\\b(?:(optional)[\\s\\t]+)?(function|sub)[\\s\\t]+([a-z0-9_]+)(\\())(\\))[\\s\\t]",
             "captures": {
                 "1": {
-                    "name": "storage.type.function.brs"
+                    "name": "storage.modifier.brs"
                 },
                 "2": {
-                    "name": "entity.name.function.member.brs"
+                    "name": "storage.type.function.brs"
                 },
                 "3": {
-                    "name": "punctuation.definition.parameters.begin.brs"
+                    "name": "entity.name.function.member.brs"
                 },
                 "4": {
-                    "name": "punctuation.definition.parameters.end.brs"
+                    "name": "punctuation.definition.parameters.begin.brs"
                 },
                 "5": {
-                    "name": "keyword.control.as.brs"
+                    "name": "punctuation.definition.parameters.end.brs"
                 }
             }
         },
         "interface_function_with_return_type": {
-            "begin": "(?i:\\s*\\b(function|sub)[\\s\\t]+([a-z0-9_]+)(\\()).*?(\\))[\\s\\t]+(as)",
+            "begin": "(?i:\\s*\\b(?:(optional)[\\s\\t]+)?(function|sub)[\\s\\t]+([a-z0-9_]+)(\\()).*?(\\))[\\s\\t]+(as)",
             "beginCaptures": {
                 "1": {
-                    "name": "storage.type.function.brs"
+                    "name": "storage.modifier.brs"
                 },
                 "2": {
-                    "name": "entity.name.function.member.brs"
+                    "name": "storage.type.function.brs"
                 },
                 "3": {
-                    "name": "punctuation.definition.parameters.begin.brs"
+                    "name": "entity.name.function.member.brs"
                 },
                 "4": {
-                    "name": "punctuation.definition.parameters.end.brs"
+                    "name": "punctuation.definition.parameters.begin.brs"
                 },
                 "5": {
+                    "name": "punctuation.definition.parameters.end.brs"
+                },
+                "6": {
                     "name": "keyword.control.as.brs"
                 }
             },
@@ -949,7 +955,7 @@
                     "name": "keyword.control.brs"
                 }
             },
-            "match": "(?i:[^\\.\\w\\\"](then|stop|run|end|each|next|throw)(?!(\\s*:)|[\\d\\w_]))"
+            "match": "(?i:[^\\.\\w\\\"](then|stop|run|end(?!\\s+(?:sub|function))|each|next|throw)(?!(\\s*:)|[\\d\\w_]))"
         },
         "loop_keywords": {
             "match": "(?i:(?<!\\.)(continue\\s+(for|while)\\b))",