diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.0.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.0.ddl.sqlpp
new file mode 100644
index 0000000..5a5bbec
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.0.ddl.sqlpp
@@ -0,0 +1,26 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+DROP DATAVERSE externallibtest if exists;
+CREATE DATAVERSE  externallibtest;
+USE externallibtest;
+
+create type CountryCapitalType if not exists as closed {
+country: string,
+capital: string
+};
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.1.lib.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.1.lib.sqlpp
new file mode 100644
index 0000000..cc6c855
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.1.lib.sqlpp
@@ -0,0 +1,19 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+install externallibtest testlib java admin admin target/data/externallib/asterix-external-data-testlib.zip
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.2.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.2.ddl.sqlpp
new file mode 100644
index 0000000..4ef5d6b
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.2.ddl.sqlpp
@@ -0,0 +1,25 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use externallibtest;
+
+create function getCapital(a: string) returns CountryCapitalType
+  as "org.apache.asterix.external.library.CapitalFinderFactory" at testlib;
+
+create function mysum(a, b) { a+b };
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.3.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.3.query.sqlpp
new file mode 100644
index 0000000..cbf2a35
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.3.query.sqlpp
@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+use externallibtest;
+
+SELECT getCapital(country) as natCap, mysum(1,2) as sum
+FROM ["England","Italy","China","United States","India","Jupiter"] as country
+ORDER BY natCap.country;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.4.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.4.ddl.sqlpp
new file mode 100644
index 0000000..65733e4
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-library/mixedudfs/mixedudfs.4.ddl.sqlpp
@@ -0,0 +1,19 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+DROP DATAVERSE externallibtest;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/mixedudfs/getCapital.1.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/mixedudfs/getCapital.1.adm
new file mode 100644
index 0000000..dd2dfbc
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-library/mixedudfs/getCapital.1.adm
@@ -0,0 +1,6 @@
+{ "natCap": { "country": "China", "capital": "Beijing" }, "sum": 3 }
+{ "natCap": { "country": "England", "capital": "London" }, "sum": 3 }
+{ "natCap": { "country": "India", "capital": "New Delhi" }, "sum": 3 }
+{ "natCap": { "country": "Italy", "capital": "Rome" }, "sum": 3 }
+{ "natCap": { "country": "Jupiter", "capital": "NOT_FOUND" }, "sum": 3 }
+{ "natCap": { "country": "United States", "capital": "Washington D.C." }, "sum": 3 }
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_it_sqlpp.xml b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_it_sqlpp.xml
index 85fe2c5..7667bb4 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_it_sqlpp.xml
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_it_sqlpp.xml
@@ -108,6 +108,11 @@
       </compilation-unit>
     </test-case>
     <test-case FilePath="external-library">
+      <compilation-unit name="mixedudfs">
+        <output-dir compare="Text">mixedudfs</output-dir>
+      </compilation-unit>
+    </test-case>
+    <test-case FilePath="external-library">
       <compilation-unit name="udf_metadata">
         <output-dir compare="Text">udf_metadata</output-dir>
       </compilation-unit>
diff --git a/asterixdb/asterix-lang-common/src/main/java/org/apache/asterix/lang/common/visitor/AbstractInlineUdfsVisitor.java b/asterixdb/asterix-lang-common/src/main/java/org/apache/asterix/lang/common/visitor/AbstractInlineUdfsVisitor.java
index 7fe7140..52775d3 100644
--- a/asterixdb/asterix-lang-common/src/main/java/org/apache/asterix/lang/common/visitor/AbstractInlineUdfsVisitor.java
+++ b/asterixdb/asterix-lang-common/src/main/java/org/apache/asterix/lang/common/visitor/AbstractInlineUdfsVisitor.java
@@ -316,7 +316,8 @@
         } else {
             FunctionDecl implem = usedUDFs.get(fs);
             if (implem == null) {
-                throw new CompilationException(ErrorCode.UNKNOWN_FUNCTION, f.getSourceLocation(), fs.toString());
+                //it's an external UDF
+                return new Pair<>(r, expr);
             }
             // it's one of the functions we want to inline
             boolean isVarargs = implem.getSignature().getArity() == FunctionIdentifier.VARARGS;