diff --git a/moonscript/transform/statement.lua b/moonscript/transform/statement.lua
index 47dd0de..7303666 100644
--- a/moonscript/transform/statement.lua
+++ b/moonscript/transform/statement.lua
@@ -484,17 +484,35 @@ return Transformer({
     return wrapped
   end,
   unless = function(self, node)
-    return {
-      "if",
-      {
-        "not",
+    local clause = node[2]
+    if ntype(clause) == "assign" then
+      if destructure.has_destructure(clause[2]) then
+        error("destructure not allowed in unless assignment")
+      end
+      return build["do"]({
+        clause,
         {
-          "parens",
-          node[2]
+          "if",
+          {
+            "not",
+            clause[2][1]
+          },
+          unpack(node, 3)
         }
-      },
-      unpack(node, 3)
-    }
+      })
+    else
+      return {
+        "if",
+        {
+          "not",
+          {
+            "parens",
+            clause
+          }
+        },
+        unpack(node, 3)
+      }
+    end
   end,
   ["if"] = function(self, node, ret)
     if ntype(node[2]) == "assign" then
diff --git a/moonscript/transform/statement.moon b/moonscript/transform/statement.moon
index 42c3ec7..f5cf3a5 100644
--- a/moonscript/transform/statement.moon
+++ b/moonscript/transform/statement.moon
@@ -280,7 +280,19 @@ Transformer {
     wrapped
 
   unless: (node) =>
-    { "if", {"not", {"parens", node[2]}}, unpack node, 3 }
+    clause = node[2]
+
+    if ntype(clause) == "assign"
+      if destructure.has_destructure clause[2]
+        error "destructure not allowed in unless assignment"
+
+      build.do {
+        clause
+        { "if", {"not", clause[2][1]}, unpack node, 3 }
+      }
+
+    else
+      { "if", {"not", {"parens", clause}}, unpack node, 3 }
 
   if: (node, ret) =>
     -- expand assign in cond
@@ -300,7 +312,7 @@ Transformer {
         }
       else
         name = assign[2][1]
-        return build["do"] {
+        return build.do {
           assign
           {"if", name, unpack node, 3}
         }
diff --git a/spec/inputs/cond.moon b/spec/inputs/cond.moon
index 3bf966f..18e42b9 100644
--- a/spec/inputs/cond.moon
+++ b/spec/inputs/cond.moon
@@ -147,6 +147,14 @@ print "hello" unless value
 
 dddd = {1,2,3} unless value
 
+
+-- 
+
+do
+  j = 100
+  unless j = hi!
+    error "not j!"
+
 ----------------
 
 a = 12
diff --git a/spec/outputs/cond.lua b/spec/outputs/cond.lua
index 30e8762..35e7ac5 100644
--- a/spec/outputs/cond.lua
+++ b/spec/outputs/cond.lua
@@ -246,6 +246,15 @@ if not (value) then
     3
   }
 end
+do
+  local j = 100
+  do
+    j = hi()
+    if not j then
+      error("not j!")
+    end
+  end
+end
 local a = 12
 local c, b
 if something then