diff --git a/complex/add.js b/complex/add.js
index fc07a9c..a831574 100644
--- a/complex/add.js
+++ b/complex/add.js
@@ -13,6 +13,7 @@ export default function create(pmath) {
            }
            if (resolve && Math.abs(sum.im/sum.re) < 1e-10) return sum.re
            return sum
-       }])
+       }],
+    create, pmath) // register ourselves for invalidation and reconfiguration
 }
                          
diff --git a/picomathInstance.js b/picomathInstance.js
index 759d215..90e4041 100644
--- a/picomathInstance.js
+++ b/picomathInstance.js
@@ -2,23 +2,43 @@
 import poortf from './poortf.js'
 
 export default function picomathInstance (instName, config) {
-    /* Since we have to do it all the time, when we call a picomath instance
-     * as a function, it takes a name and 0 or more implementations add adds
-     * them to its poortf property named name, returning that property value.
-     */
-    function fn (name, imps, author, data) {
-        if (name in fn) {
-            fn[name].addImps(imps, author, data)
-        } else {
-            fn[name] = poortf(name, imps, author, data)
-        }
-        return fn[name]
-    }
+   /* Since we have to do it all the time, when we call a picomath instance
+    * as a function, it takes a name and 0 or more implementations add adds
+    * them to its poortf property named name, returning that property value.
+    */
+   function fn (name, imps, author, data) {
+      if (name in fn) {
+         fn[name].addImps(imps, author, data)
+      } else {
+         fn[name] = poortf(name, imps, author, data)
+      }
+      /* For PoC, just assume only reason to provide author info
+       * is to be invalidated when config changes
+       */
+      if (author) {
+         if (!fn.configUsers.has(author)) {
+            fn.configUsers.set(author, new Set())
+         }
+         fn.configUsers.get(author).add(name)
+      }
+      return fn[name]
+   }
 
-    Object.defineProperty(fn, 'name', {value: instName})
-    fn.config = config || { resolveComplex: false } // primitive default for POC
-
-    return fn
+   Object.defineProperty(fn, 'name', {value: instName})
+   // There is an issue below of possible collision between the following
+   // property names and operation names. Since it would not be too hard to
+   // solve, we won't worry about it in this PoC.
+   fn.config = config || { resolveComplex: false } // primitive default for POC
+   fn.configUsers = new Map()
+   fn.reconfigure = config => {
+      for (const [author, names] of fn.configUsers.entries()) {
+         for (const name of names) {
+            fn[name].invalidate(author)
+         }
+      }
+      fn.config = config
+   }
+   return fn
 }
 
     
diff --git a/test/custom.js b/test/custom.js
index 69ac993..1107800 100644
--- a/test/custom.js
+++ b/test/custom.js
@@ -46,4 +46,10 @@ describe('Custom instances', () => {
       assert.deepStrictEqual(math.add(math.complex(2,3), math.complex(2,-3)),
          math.complex(4,0))
    })
+
+   it("can be reconfigured", () => {
+      res.reconfigure({resolveComplex: false})
+      assert.deepStrictEqual(math.add(math.complex(2,3), math.complex(2,-3)),
+         math.complex(4,0))
+   })
 })