diff --git a/lib/typeprof/core/ast.rb b/lib/typeprof/core/ast.rb
index 8420c3881..e08a4ac87 100644
--- a/lib/typeprof/core/ast.rb
+++ b/lib/typeprof/core/ast.rb
@@ -362,7 +362,7 @@ def self.create_pattern_node(raw_node, lenv)
 
       when :capture_pattern_node then CapturePatternNode.new(raw_node, lenv)
 
-      when :if_node then IfPatternNode.new(raw_node, lenv)
+      when :if_node, :unless_node then IfPatternNode.new(raw_node, lenv)
 
       when :pinned_variable_node then PinnedPatternNode.new(raw_node, lenv)
       when :pinned_expression_node then PinnedPatternNode.new(raw_node, lenv)
diff --git a/lib/typeprof/core/ast/pattern.rb b/lib/typeprof/core/ast/pattern.rb
index 29473e3ed..eed2da948 100644
--- a/lib/typeprof/core/ast/pattern.rb
+++ b/lib/typeprof/core/ast/pattern.rb
@@ -144,7 +144,8 @@ def initialize(raw_node, lenv)
         raise if raw_node.statements.type != :statements_node
         raise if raw_node.statements.body.size != 1
         @body = AST.create_pattern_node(raw_node.statements.body[0], lenv)
-        raise if raw_node.subsequent
+        raise if raw_node.type == :if_node && raw_node.subsequent
+        raise if raw_node.type == :unless_node && raw_node.else_clause
       end
 
       attr_reader :cond, :body
diff --git a/scenario/patterns/unless_pat.rb b/scenario/patterns/unless_pat.rb
new file mode 100644
index 000000000..11c0157c7
--- /dev/null
+++ b/scenario/patterns/unless_pat.rb
@@ -0,0 +1,17 @@
+## update: test.rb
+def cond?(x)
+  x
+end
+
+def check(x)
+  case x
+  in 1 unless cond?(:ok)
+    :ok
+  end
+end
+
+## assert
+class Object
+  def cond?: (:ok) -> :ok
+  def check: (untyped) -> :ok
+end