diff --git a/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/am/AccessMethodUtils.java b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/am/AccessMethodUtils.java
index 3215707..6651ea3 100644
--- a/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/am/AccessMethodUtils.java
+++ b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/am/AccessMethodUtils.java
@@ -220,7 +220,7 @@
             return new ConstantExpression(optFuncExpr.getConstantVal(0));
         } else {
             // We are optimizing a join query. Determine which variable feeds the secondary index. 
-            if (optFuncExpr.getOperatorSubTree(0) == probeSubTree) {
+            if (optFuncExpr.getOperatorSubTree(0) == null || optFuncExpr.getOperatorSubTree(0) == probeSubTree) {
                 return new VariableReferenceExpression(optFuncExpr.getLogicalVar(0));
             } else {
                 return new VariableReferenceExpression(optFuncExpr.getLogicalVar(1));
diff --git a/asterix-app/src/test/resources/optimizerts/queries/btree-index-join/secondary-equi-join-multiindex.aql b/asterix-app/src/test/resources/optimizerts/queries/btree-index-join/secondary-equi-join-multiindex.aql
new file mode 100644
index 0000000..44cdef8
--- /dev/null
+++ b/asterix-app/src/test/resources/optimizerts/queries/btree-index-join/secondary-equi-join-multiindex.aql
@@ -0,0 +1,60 @@
+/*
+ * Description    : Equi joins two datasets, FacebookUsers and FacebookMessages, based on their user's id.
+ *                  We first expect FacebookUsers' primary index to be used 
+ *                  to satisfy the range condition on it's primary key. 
+ *                  FacebookMessages has a secondary btree index on author-id-copy, and given the 'indexnl' hint 
+ *                  we expect the join to be transformed into an indexed nested-loop join.
+ * Success        : Yes
+ */
+
+drop dataverse test if exists;
+create dataverse test;
+use dataverse test;
+
+create type EmploymentType as closed { 
+  organization-name: string,
+  start-date: date,
+  end-date: date?
+} 
+
+create type FacebookUserType as closed { 
+  id: int32,
+  id-copy: int32,
+  alias: string,
+  name: string,
+  user-since: datetime,
+  user-since-copy: datetime,
+  friend-ids: {{ int32 }},
+  employment: [EmploymentType]
+} 
+
+create type FacebookMessageType as closed { 
+  message-id: int32,
+  message-id-copy: int32,
+  author-id: int32,
+  author-id-copy: int32,
+  in-response-to: int32?,
+  sender-location: point?,
+  message: string
+} 
+
+create dataset FacebookUsers(FacebookUserType)
+partitioned by key id;
+
+create dataset FacebookMessages(FacebookMessageType)
+partitioned by key message-id;
+
+create index fbmIdxAutId if not exists on FacebookMessages(author-id-copy);
+
+write output to nc1:"rttest/btree-index-join_title-secondary-equi-join-multiindex.adm";
+
+for $user in dataset('FacebookUsers')
+for $message in dataset('FacebookMessages')
+where $user.id /*+ indexnl */ = $message.author-id-copy
+and $user.id >= 11000 and $user.id <= 12000
+return {
+  "fbu-ID": $user.id,
+  "fbm-auth-ID": $message.author-id,
+  "uname": $user.name,
+  "message": $message.message
+}
diff --git a/asterix-app/src/test/resources/optimizerts/results/btree-index-join/secondary-equi-join-multiindex.plan b/asterix-app/src/test/resources/optimizerts/results/btree-index-join/secondary-equi-join-multiindex.plan
new file mode 100644
index 0000000..76a5aa8
--- /dev/null
+++ b/asterix-app/src/test/resources/optimizerts/results/btree-index-join/secondary-equi-join-multiindex.plan
@@ -0,0 +1,19 @@
+-- SINK_WRITE  |PARTITIONED|
+  -- RANDOM_MERGE_EXCHANGE  |PARTITIONED|
+    -- STREAM_PROJECT  |PARTITIONED|
+      -- ASSIGN  |PARTITIONED|
+        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+          -- BTREE_SEARCH  |PARTITIONED|
+            -- ONE_TO_ONE_EXCHANGE  |LOCAL|
+              -- STABLE_SORT [$$29(ASC)]  |LOCAL|
+                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                  -- STREAM_PROJECT  |PARTITIONED|
+                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                      -- BTREE_SEARCH  |PARTITIONED|
+                        -- BROADCAST_EXCHANGE  |PARTITIONED|
+                          -- ASSIGN  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- BTREE_SEARCH  |PARTITIONED|
+                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                  -- ASSIGN  |PARTITIONED|
+                                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
\ No newline at end of file
diff --git a/asterix-metadata/src/main/java/edu/uci/ics/asterix/metadata/declared/AqlMetadataProvider.java b/asterix-metadata/src/main/java/edu/uci/ics/asterix/metadata/declared/AqlMetadataProvider.java
index 4f8e467..fad1731 100644
--- a/asterix-metadata/src/main/java/edu/uci/ics/asterix/metadata/declared/AqlMetadataProvider.java
+++ b/asterix-metadata/src/main/java/edu/uci/ics/asterix/metadata/declared/AqlMetadataProvider.java
@@ -409,7 +409,7 @@
                         dataset.getDatasetName(), indexName);
                 int numSecondaryKeys = secondaryIndex.getKeyFieldNames().size();
                 numKeys += numSecondaryKeys;
-                keysStartIndex = outputRecDesc.getFieldCount() - numKeys;
+                keysStartIndex = outputVars.size() - numKeys;
             }
             IBinaryComparatorFactory[] comparatorFactories = JobGenHelper.variablesToAscBinaryComparatorFactories(
                     outputVars, keysStartIndex, numKeys, typeEnv, context);