2 files changed, 6 insertions, 0 deletions
diff --git a/ext/dl/lib/dl/func.rb b/ext/dl/lib/dl/func.rb
index 1ec34b7cf3..7a8b62e325 100644
--- a/ext/dl/lib/dl/func.rb
+++ b/ext/dl/lib/dl/func.rb
@@ -95,6 +95,10 @@ module DL
       end
     end
 
+    def bound?()
+      @cfunc.ptr != 0
+    end
+
     def bind_at_call(&block)
       bind(&block)
     end
diff --git a/ext/dl/lib/dl/value.rb b/ext/dl/lib/dl/value.rb
index bb8348cf5e..56dfcefa32 100644
--- a/ext/dl/lib/dl/value.rb
+++ b/ext/dl/lib/dl/value.rb
@@ -63,6 +63,8 @@ module DL
           if( block )
             arg.bind_at_call(&block)
             funcs.push(arg)
+          elsif !arg.bound?
+            raise(RuntimeError, "block must be given.")
           end
           return arg.to_i
         when String