diff --git a/lib/arch.js b/lib/arch.js
index 88747c7..7b0dd1b 100644
--- a/lib/arch.js
+++ b/lib/arch.js
@@ -250,14 +250,16 @@ module.exports = INHERIT({
 
         for (var i = 0; i < parents.length; i++) {
             parent = parents[i];
-            children = this.children[parent] || (this.children[parent] = []);
+            if (!this.hasParents(child, parent)) {
+                children = this.children[parent] || (this.children[parent] = []);
 
-            if (_parents.indexOf(parent) === -1) _parents.push(parent);
-            if (children.indexOf(child) === -1) children.push(child);
+                if (_parents.indexOf(parent) === -1) _parents.push(parent);
+                if (children.indexOf(child) === -1) children.push(child);
 
-            for (var k in this.plans) {
-                var p = this.plans[k];
-                if (p.hasNode(child) || p.hasNode(parent)) p.link(child, parent);
+                for (var k in this.plans) {
+                    var p = this.plans[k];
+                    if (p.hasNode(child) || p.hasNode(parent)) p.link(child, parent);
+                }
             }
         }
     },
diff --git a/test/arch-test.js b/test/arch-test.js
index ba6a32f..51e4816 100644
--- a/test/arch-test.js
+++ b/test/arch-test.js
@@ -139,6 +139,7 @@ suite
                 arch.setNode('A', { run: 'testA' });
                 arch.setNode('B', { run: 'testA' });
                 arch.link('B', 'A');
+                arch.link('B', 'A');
                 
                 return arch;
             },
@@ -162,6 +163,7 @@ suite
                 arch.setNode('A', { run: 'testA' });
                 arch.setNode('B', { run: 'testB' }, 'A');
                 arch.unlink('B', 'A');
+                arch.unlink('B', 'A');
 
                 return arch;
             },