diff --git a/src/filter/graph.rs b/src/filter/graph.rs
index 1654e6e1..b63cd6cb 100644
--- a/src/filter/graph.rs
+++ b/src/filter/graph.rs
@@ -161,7 +161,13 @@ impl<'a> Parser<'a> {
             if self.inputs.is_null() {
                 self.inputs = input;
             } else {
-                (*self.inputs).next = input;
+                let mut prev_input = self.inputs;
+                let mut next_input = (*prev_input).next;
+                while !next_input.is_null() {
+                    prev_input = next_input;
+                    next_input = (*next_input).next;
+                }
+                (*prev_input).next = input;
             }
         }
 
@@ -187,7 +193,13 @@ impl<'a> Parser<'a> {
             if self.outputs.is_null() {
                 self.outputs = output;
             } else {
-                (*self.outputs).next = output;
+                let mut prev_output = self.outputs;
+                let mut next_output = (*prev_output).next;
+                while !next_output.is_null() {
+                    prev_output = next_output;
+                    next_output = (*next_output).next;
+                }
+                (*prev_output).next = output;
             }
         }