diff --git a/common.js b/common.js
index e95ea5b..eae7c05 100644
--- a/common.js
+++ b/common.js
@@ -40,5 +40,28 @@ function checkIssuerToken(req, expectedSub) {
   });
 }
 
+async function getPrimarySub(grantStore, secondary) {
+  var results = await Promise.all([
+    grantStore.find({ sub:    secondary }),
+    grantStore.find({ azpSub: secondary }),
+  ]);
+
+  // Extract only the sub field from each row and reduce the duplicates so that each value
+  // can only appear in the final list once.
+  var subList = [].concat.apply([], results).map(grant => grant.sub);
+  subList = subList.filter((sub, ind, list) => list.indexOf(sub) === ind);
+
+  if (subList.length > 1) {
+    // This should not ever happen since there is a check for PPID collisions when saving
+    // grants, but it's probably better to have this check anyway just incase something
+    // happens that isn't currently accounted for.
+    console.error('acounts ' + JSON.stringify(subList) + ' are all associated with "'+secondary+'"');
+    throw new Error('PPID collision');
+  }
+
+  return subList[0];
+}
+
 module.exports.checkIssuerToken = checkIssuerToken;
+module.exports.getPrimarySub = getPrimarySub;
 module.exports.makeB64UrlSafe = makeB64UrlSafe;
diff --git a/grants.js b/grants.js
index dec2d1d..2fe161a 100644
--- a/grants.js
+++ b/grants.js
@@ -56,14 +56,16 @@ function create(app) {
         throw new OpErr("malformed request: 'sub' and 'scope' must be strings");
       }
 
-      return req.Store.find({ azpSub: req.body.sub });
-    }).then(function (existing) {
-      if (existing.length) {
-        if (existing.length > 1) {
-          throw new OpErr("pre-existing PPID collision detected");
-        } else if (existing[0].sub !== req.params.sub || existing[0].azp !== req.params.azp) {
-          throw new OpErr("PPID collision detected, cannot save authorized party's sub");
+      return require('./common').getPrimarySub(req.Store, req.body.sub).catch(function (err) {
+        if (/collision/.test(err.message)) {
+          err.message = 'pre-existing PPID collision detected';
         }
+        throw err;
+      });
+    }).then(function (primSub) {
+      if (primSub && primSub !== req.params.sub) {
+        console.log('account "'+req.params.sub+'" cannot use PPID "'+req.body.sub+'" already used by "'+primSub+'"');
+        throw new OpErr("PPID collision detected, cannot save authorized party's sub");
       }
 
       var grant = {
diff --git a/jwks.js b/jwks.js
index c769f09..0be4092 100644
--- a/jwks.js
+++ b/jwks.js
@@ -62,26 +62,21 @@ function create(app) {
     }
 
     // The keys are stored by the issuer PPID, but the sub we have might be a different PPID
-    // for a 3rd party. As such we need to look up the subject in the grants to get the issuer
-    // PPID and to make sure there wasn't some kind of error that allowed multiple users to
-    // somehow use the same PPID.
-    var results = await Promise.all([
-      store.IssuerOauth3OrgGrants.find({ sub:    req.params.sub }),
-      store.IssuerOauth3OrgGrants.find({ azpSub: req.params.sub }),
-    ]);
-    var subList = [].concat.apply([], results).map(grant => grant.sub);
-    subList = subList.filter((sub, ind, list) => list.indexOf(sub) === ind);
-    if (!subList.length) {
-      throw new OpErr("unknown PPID '" + req.params.sub + "'");
-    }
-    if (subList.length > 1) {
-      // This should not ever happen since there is a check for PPID collisions when saving
-      // grants, but it's probably better to have this check anyway just incase something
-      // happens that isn't currently accounted for.
-      throw new OpErr('PPID collision - unable to safely retrieve keys');
+    // for a 3rd party.
+    var issuerSub;
+    try {
+      issuerSub = await require('./common').getPrimarySub(store.IssuerOauth3OrgGrants, req.params.sub);
+    } catch (err) {
+      if (/collision/.test(err.message)) {
+        err.message = 'PPID collision - unable to safely retrieve keys';
+      }
+      throw err;
     }
 
-    return store.IssuerOauth3OrgJwks.get(subList[0] + '/' + req.params.kid);
+    if (!issuerSub) {
+      throw new OpErr("unknown PPID '" + req.params.sub + "'");
+    }
+    return store.IssuerOauth3OrgJwks.get(issuerSub + '/' + req.params.kid);
   }
 
   restful.get = function (req, res) {