diff --git a/.travis.yml b/.travis.yml
index d990cf834471e84db73561f3ad4e2d63202c5068..37bf1b94e6e365ee85d214f4f8d1e7ce2d915a4e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,7 @@ php:
   - 7.0
   - 7.1
   - 7.2
+  - 7.3
 
 env:
   - VUFIND_HOME=$PWD VUFIND_LOCAL_DIR=$PWD/local
diff --git a/module/VuFind/src/VuFind/Search/Solr/SpellingProcessor.php b/module/VuFind/src/VuFind/Search/Solr/SpellingProcessor.php
index 03720d3fbc75c857d3efacee16fa1703ab5a9144..357f1fce804ea74a08574516807314799324391e 100644
--- a/module/VuFind/src/VuFind/Search/Solr/SpellingProcessor.php
+++ b/module/VuFind/src/VuFind/Search/Solr/SpellingProcessor.php
@@ -252,7 +252,7 @@ class SpellingProcessor
             foreach ($this->tokenize($query) as $token) {
                 // TODO - Do we need stricter matching here, similar to that in
                 // \VuFindSearch\Query\Query::replaceTerm()?
-                if (stripos($token, $term) !== false) {
+                if (stripos($token, (string)$term) !== false) {
                     $inToken = true;
                     // We need to replace the whole token
                     $targetTerm = $token;