diff --git a/.changeset/stale-impalas-visit.md b/.changeset/stale-impalas-visit.md
new file mode 100644
index 00000000..06c542de
--- /dev/null
+++ b/.changeset/stale-impalas-visit.md
@@ -0,0 +1,5 @@
+---
+"htmljs-parser": patch
+---
+
+Fix regression where the parser would continue unary keyword expressions even if the keyword was inside a word boundary. Eg `<div class=thing_new x>` would cause the parser to see the expression as `thing_` and `new x`.
diff --git a/src/__tests__/fixtures/attr-complex-unary/__snapshots__/attr-complex-unary.expected.txt b/src/__tests__/fixtures/attr-complex-unary/__snapshots__/attr-complex-unary.expected.txt
new file mode 100644
index 00000000..75c9de49
--- /dev/null
+++ b/src/__tests__/fixtures/attr-complex-unary/__snapshots__/attr-complex-unary.expected.txt
@@ -0,0 +1,80 @@
+1╭─ tag a = class b {}
+ │  │   │ │ ╰─ attrValue.value "class b {}"
+ │  │   │ ╰─ attrValue "= class b {}"
+ │  │   ╰─ attrName
+ ╰─ ╰─ tagName "tag"
+2╭─ 
+ ╰─ ╰─ openTagEnd
+3╭─ tag a = class, b
+ │  │   │ │ │      ╰─ attrName
+ │  │   │ │ ╰─ attrValue.value "class"
+ │  │   │ ╰─ attrValue "= class"
+ │  │   ╰─ attrName
+ │  ├─ closeTagEnd(tag)
+ ╰─ ╰─ tagName "tag"
+4╭─ 
+ ╰─ ╰─ openTagEnd
+5╭─ <tag a = class></tag>
+ │  ││   │ │ │    ││ │  ╰─ closeTagEnd(tag)
+ │  ││   │ │ │    ││ ╰─ closeTagName "tag"
+ │  ││   │ │ │    │╰─ closeTagStart "</"
+ │  ││   │ │ │    ╰─ openTagEnd
+ │  ││   │ │ ╰─ attrValue.value "class"
+ │  ││   │ ╰─ attrValue "= class"
+ │  ││   ╰─ attrName
+ │  │╰─ tagName "tag"
+ │  ├─ closeTagEnd(tag)
+ ╰─ ╰─ openTagStart
+6├─ 
+7╭─ <tag a = class/>
+ │  ││   │ │ │    ╰─ openTagEnd:selfClosed "/>"
+ │  ││   │ │ ╰─ attrValue.value "class"
+ │  ││   │ ╰─ attrValue "= class"
+ │  ││   ╰─ attrName
+ │  │╰─ tagName "tag"
+ ╰─ ╰─ openTagStart
+8├─ 
+9╭─ tag a = classthing b
+ │  │   │ │ │          ╰─ attrName
+ │  │   │ │ ╰─ attrValue.value "classthing"
+ │  │   │ ╰─ attrValue "= classthing"
+ │  │   ╰─ attrName
+ ╰─ ╰─ tagName "tag"
+10╭─ 
+  ╰─ ╰─ openTagEnd
+11╭─ tag a = testclass b
+  │  │   │ │ │         ╰─ attrName
+  │  │   │ │ ╰─ attrValue.value "testclass"
+  │  │   │ ╰─ attrValue "= testclass"
+  │  │   ╰─ attrName
+  │  ├─ closeTagEnd(tag)
+  ╰─ ╰─ tagName "tag"
+12╭─ 
+  ╰─ ╰─ openTagEnd
+13╭─ tag a = test_class b
+  │  │   │ │ │          ╰─ attrName
+  │  │   │ │ ╰─ attrValue.value "test_class"
+  │  │   │ ╰─ attrValue "= test_class"
+  │  │   ╰─ attrName
+  │  ├─ closeTagEnd(tag)
+  ╰─ ╰─ tagName "tag"
+14╭─ 
+  ╰─ ╰─ openTagEnd
+15╭─ tag a = test$class b
+  │  │   │ │ │          ╰─ attrName
+  │  │   │ │ ╰─ attrValue.value "test$class"
+  │  │   │ ╰─ attrValue "= test$class"
+  │  │   ╰─ attrName
+  │  ├─ closeTagEnd(tag)
+  ╰─ ╰─ tagName "tag"
+16╭─ 
+  ╰─ ╰─ openTagEnd
+17╭─ tag a = test+class b
+  │  │   │ │ ╰─ attrValue.value "test+class b"
+  │  │   │ ╰─ attrValue "= test+class b"
+  │  │   ╰─ attrName
+  │  ├─ closeTagEnd(tag)
+  ╰─ ╰─ tagName "tag"
+18╭─ 
+  │  ├─ openTagEnd
+  ╰─ ╰─ closeTagEnd(tag)
\ No newline at end of file
diff --git a/src/__tests__/fixtures/attr-complex-unary/input.marko b/src/__tests__/fixtures/attr-complex-unary/input.marko
new file mode 100644
index 00000000..e9e73b2e
--- /dev/null
+++ b/src/__tests__/fixtures/attr-complex-unary/input.marko
@@ -0,0 +1,17 @@
+tag a = class b {}
+
+tag a = class, b
+
+<tag a = class></tag>
+
+<tag a = class/>
+
+tag a = classthing b
+
+tag a = testclass b
+
+tag a = test_class b
+
+tag a = test$class b
+
+tag a = test+class b
diff --git a/src/states/EXPRESSION.ts b/src/states/EXPRESSION.ts
index d1954cbf..a0e91bfa 100644
--- a/src/states/EXPRESSION.ts
+++ b/src/states/EXPRESSION.ts
@@ -296,7 +296,8 @@ function lookBehindForOperator(data: string, pos: number): number {
       for (const keyword of unaryKeywords) {
         const keywordPos = lookBehindFor(data, curPos, keyword);
         if (keywordPos !== -1) {
-          return data.charCodeAt(keywordPos - 1) === CODE.PERIOD
+          const prevCode = data.charCodeAt(keywordPos - 1);
+          return prevCode === CODE.PERIOD || isWordCode(prevCode)
             ? -1
             : keywordPos;
         }