diff --git a/src/core/PocomathInstance.mjs b/src/core/PocomathInstance.mjs
index b1b865d..8cb572b 100644
--- a/src/core/PocomathInstance.mjs
+++ b/src/core/PocomathInstance.mjs
@@ -31,6 +31,13 @@ export default class PocomathInstance {
        */
       this.Types = {any: anySpec, T: anySpec}
       this._subtypes = {} // For each type, gives all of its (in)direct subtypes
+      /* The following gives for each type, a set of all types that could
+       * match in typed-function's dispatch algorithm before the given type.
+       * This is important because if we instantiate a template, we must
+       * instantiate it for all prior types as well, or else the wrong instance
+       * might match.
+       */
+      this._priorTypes = {}
       this._usedTypes = new Set() // all types that have occurred in a signature
       this._doomed = new Set() // for detecting circular reference
       this._config = {predictable: false}
@@ -170,7 +177,12 @@ export default class PocomathInstance {
                   const mod = await import(modName)
                   this.install(mod)
                } catch (err) {
-                  // No such module, but that's OK
+                  if (!(err.message.includes('find'))) {
+                     // Not just a error because module doesn't exist
+                     // So take it seriously
+                     throw err
+                  }
+                  // We don't care if a module doesn't exist, so merely proceed
                }
             }
             doneSet.add(name)
@@ -235,6 +247,7 @@ export default class PocomathInstance {
       }
       this._typed.addTypes([{name: type, test: testFn}], beforeType)
       this.Types[type] = spec
+      this._priorTypes[type] = new Set()
       /* Now add conversions to this type */
       for (const from in (spec.from || {})) {
          if (from in this.Types) {
@@ -243,6 +256,7 @@ export default class PocomathInstance {
             while (nextSuper) {
                this._typed.addConversion(
                   {from, to: nextSuper, convert: spec.from[from]})
+               this._priorTypes[nextSuper].add(from)
                nextSuper = this.Types[nextSuper].refines
             }
          }
@@ -261,21 +275,24 @@ export default class PocomathInstance {
                   to: nextSuper,
                   convert: this.Types[to].from[type]
                })
+               this._priorTypes[nextSuper].add(type)
                nextSuper = this.Types[nextSuper].refines
             }
          }
       }
-      if (spec.refines) {
-         this._typed.addConversion(
-            {from: type, to: spec.refines, convert: x => x})
-      }
+      // Update all the subtype sets of supertypes up the chain, and
+      // while we are at it add trivial conversions from subtypes to supertypes
+      // to help typed-function match signatures properly:
       this._subtypes[type] = new Set()
-      // Update all the subtype sets of supertypes up the chain:
       let nextSuper = spec.refines
       while (nextSuper) {
+         this._typed.addConversion(
+            {from: type, to: nextSuper, convert: x => x})
+         this._priorTypes[nextSuper].add(type)
          this._subtypes[nextSuper].add(type)
          nextSuper = this.Types[nextSuper].refines
       }
+
       // rebundle anything that uses the new type:
       this._invalidateDependents(':' + type)
    }