diff --git a/core/src/test/scala/shapeless/hlistconstraints.scala b/core/src/test/scala/shapeless/hlistconstraints.scala
index 06a04de54..38913ceb9 100644
--- a/core/src/test/scala/shapeless/hlistconstraints.scala
+++ b/core/src/test/scala/shapeless/hlistconstraints.scala
@@ -19,6 +19,8 @@ package shapeless
 import org.junit.Test
 import org.junit.Assert._
 
+import shapeless.test.illTyped
+
 class HListConstraintsTests {
   @Test
   def testUnaryTCConstraint {
@@ -31,7 +33,10 @@ class HListConstraintsTests {
     val l2 = Option(23) :: true :: Option("foo") :: HNil
     
     acceptOption(l1)  // Compiles
-    //acceptOption(l2)  // Does not compile
+
+    illTyped("""
+    acceptOption(l2)
+    """)
 
     val l3 = 23 :: true :: "foo" :: HNil 
     
@@ -45,7 +50,9 @@ class HListConstraintsTests {
     def acceptConst[L <: HList : *->*[Const[String]#λ]#λ](l : L) = true
     
     acceptConst(l4)  // Compiles
-    //acceptConst(l5)  // Does not compile
+    illTyped("""
+    acceptConst(l5)
+    """)
   }
   
   @Test
@@ -60,7 +67,9 @@ class HListConstraintsTests {
     val l2 = 23 :: true :: 13 :: 7 :: 5 :: 2.0 :: "foo" :: "bar" :: HNil
 
     acceptBasis(l1) // Compiles
-    //acceptBasis(l2) // Does not compile
+    illTyped("""
+    acceptBasis(l2)
+    """)
   }
   
   @Test
@@ -77,7 +86,9 @@ class HListConstraintsTests {
     val l2 = Apple :: 23 :: "foo" :: Pear :: HNil
 
     acceptLUB(l1) // Compiles
-    //acceptLUB(l2) // Does not compile
+    illTyped("""
+    acceptLUB(l2)
+    """)
   }
 
   @Test
@@ -107,11 +118,15 @@ class HListConstraintsTests {
     def acceptKeys[R <: HList : Keys[author.type :: title.type :: id.type :: HNil]#λ](r : R) = true
     
     acceptKeys(summary)   // Compiles
-    //acceptKeys(book)    // Does not compile
+    illTyped("""
+    acceptKeys(book)
+    """)
 
     def acceptValues[R <: HList : Values[Int :: String :: HNil]#λ](r : R) = true
     
     acceptValues(summary) // Compiles
-    //acceptValues(book)  // Does not compile
+    illTyped("""
+    acceptValues(book)
+    """)
   }
 }
diff --git a/core/src/test/scala/shapeless/sized.scala b/core/src/test/scala/shapeless/sized.scala
index 491e56373..ace7327b0 100644
--- a/core/src/test/scala/shapeless/sized.scala
+++ b/core/src/test/scala/shapeless/sized.scala
@@ -19,6 +19,8 @@ package shapeless
 import org.junit.Test
 import org.junit.Assert._
 
+import shapeless.test.illTyped
+
 class SizedTests {
   import nat._
   import Sized._
@@ -41,8 +43,12 @@ class SizedTests {
     val nl0d = l0.sized(3)
     assertTrue(nl0d.isEmpty)
     
-    //val h0 = nl0.get.head // Does not compile
-    //val t0 = nl0.get.tail // Does not compile
+    illTyped("""
+    val h0 = nl0.get.head
+    """)
+    illTyped("""
+    val t0 = nl0.get.tail
+    """)
     
     val nl1 = l1.sized(0)
     assertTrue(nl1.isEmpty)
@@ -55,7 +61,10 @@ class SizedTests {
 
     val h1 = nl1b.get.head
     val t1 = nl1b.get.tail
-    //val t1b = nl1b.get.tail.tail // Does not compile
+
+    illTyped("""
+    val t1b = nl1b.get.tail.tail
+    """)
 
     val nl2 = l2.sized(0)
     assertTrue(nl2.isEmpty)
@@ -69,7 +78,10 @@ class SizedTests {
     val h2 = nl2c.get.head
     val t2 = nl2c.get.tail
     val t2b = nl2c.get.tail.tail
-    //val t2c = nl1c.get.tail.tail.tail // Does not compile
+
+    illTyped("""
+    val t2c = nl1c.get.tail.tail.tail
+    """)
 
     val nl3 = l3.sized(0)
     assertTrue(nl3.isEmpty)
@@ -84,7 +96,10 @@ class SizedTests {
     val t3 = nl3d.get.tail
     val t3b = nl3d.get.tail.tail
     val t3c = nl3d.get.tail.tail.tail
-    //val t3d = nl1d.get.tail.tail.tail.tail // Does not compile
+
+    illTyped("""
+    val t3d = nl1d.get.tail.tail.tail.tail
+    """)
     
     val rs = "foo".sized(3).get.unsized
     
@@ -138,15 +153,24 @@ class SizedTests {
     
     val tk1 = cl.get.take(1)
     val tk4 = cl.get.take(4)
-    //val tk7 = cl.get.take(7)  // Does not compile
+
+    illTyped("""
+    val tk7 = cl.get.take(7)
+    """)
     
     val dr1 = cl.get.drop(1)
     val dr4 = cl.get.drop(4)
-    //val dr7 = cl.get.drop(7)  // Does not compile
+
+    illTyped("""
+    val dr7 = cl.get.drop(7)
+    """)
     
     val (pr1, sf1) = cl.get.splitAt(1)
     val (pr4, sf4) = cl.get.splitAt(4)
-    //val (pr7, sf7) = cl.get.splitAt(7)  // Does not compile
+
+    illTyped("""
+    val (pr7, sf7) = cl.get.splitAt(7)
+    """)
     
     val ml = cl.get map (_.toString)
     typed[Sized[List[String], _6]](ml)