diff --git a/src/core/thread/fiber.d b/src/core/thread/fiber.d
index 23f49850c8..27712e81ec 100644
--- a/src/core/thread/fiber.d
+++ b/src/core/thread/fiber.d
@@ -603,14 +603,9 @@ class Fiber
      */
     this( void delegate() dg, size_t sz = PAGESIZE * defaultStackPages,
           size_t guardPageSize = PAGESIZE ) nothrow
-    in
-    {
-        assert( dg );
-    }
-    do
     {
         allocStack( sz, guardPageSize );
-        reset( dg );
+        reset( cast(void delegate() const) dg );
     }
 
 
diff --git a/src/core/thread/threadbase.d b/src/core/thread/threadbase.d
index e758bdc16e..170bb65f5e 100644
--- a/src/core/thread/threadbase.d
+++ b/src/core/thread/threadbase.d
@@ -105,8 +105,8 @@ class ThreadBase
         m_call = fn;
     }
 
-    this(void delegate() dg, size_t sz = 0) @safe pure nothrow @nogc
-    in(dg)
+    this(void delegate() dg, size_t sz = 0) @trusted pure nothrow @nogc
+    in( cast(void delegate() const) dg)
     {
         this(sz);
         m_call = dg;
diff --git a/src/object.d b/src/object.d
index c8eb7ca636..eda89a8993 100644
--- a/src/object.d
+++ b/src/object.d
@@ -1481,7 +1481,7 @@ class TypeInfo_Delegate : TypeInfo
 
     override size_t getHash(scope const void* p) @trusted const
     {
-        return hashOf(*cast(void delegate()*)p);
+        return hashOf(*cast(void delegate() const *)p);
     }
 
     override bool equals(in void* p1, in void* p2) const