diff --git a/data-index/data-index-common/src/main/resources/basic.schema.graphqls b/data-index/data-index-common/src/main/resources/basic.schema.graphqls
index f6d22aa649..8c7f07a197 100644
--- a/data-index/data-index-common/src/main/resources/basic.schema.graphqls
+++ b/data-index/data-index-common/src/main/resources/basic.schema.graphqls
@@ -1,6 +1,7 @@
 scalar DateTime
 scalar BigDecimal
 scalar Long
+scalar JSON
 
 schema {
     query: Query
@@ -25,7 +26,7 @@ type ProcessInstance {
     serviceUrl: String
     nodes: [NodeInstance!]!
     milestones: [Milestone!]
-    variables: String
+    variables: JSON
     start: DateTime!
     end: DateTime
     parentProcessInstance: ProcessInstance
diff --git a/data-index/data-index-service/data-index-service-common/src/main/java/org/kie/kogito/index/service/graphql/GraphQLSchemaManagerImpl.java b/data-index/data-index-service/data-index-service-common/src/main/java/org/kie/kogito/index/service/graphql/GraphQLSchemaManagerImpl.java
index 5518de4942..36f9298739 100644
--- a/data-index/data-index-service/data-index-service-common/src/main/java/org/kie/kogito/index/service/graphql/GraphQLSchemaManagerImpl.java
+++ b/data-index/data-index-service/data-index-service-common/src/main/java/org/kie/kogito/index/service/graphql/GraphQLSchemaManagerImpl.java
@@ -144,6 +144,7 @@ public GraphQLSchema createSchema() {
                 .scalar(getDateTimeScalarType())
                 .scalar(ExtendedScalars.GraphQLBigDecimal)
                 .scalar(ExtendedScalars.GraphQLLong)
+                .scalar(ExtendedScalars.Json)
                 .build();
 
         SchemaGenerator schemaGenerator = new SchemaGenerator();
diff --git a/data-index/kogito-addons-quarkus-data-index/kogito-addons-quarkus-data-index-common/runtime/src/main/java/org/kie/kogito/index/addon/graphql/GraphQLAddonSchemaManagerImpl.java b/data-index/kogito-addons-quarkus-data-index/kogito-addons-quarkus-data-index-common/runtime/src/main/java/org/kie/kogito/index/addon/graphql/GraphQLAddonSchemaManagerImpl.java
index d3f4c10f29..e5146a109b 100644
--- a/data-index/kogito-addons-quarkus-data-index/kogito-addons-quarkus-data-index-common/runtime/src/main/java/org/kie/kogito/index/addon/graphql/GraphQLAddonSchemaManagerImpl.java
+++ b/data-index/kogito-addons-quarkus-data-index/kogito-addons-quarkus-data-index-common/runtime/src/main/java/org/kie/kogito/index/addon/graphql/GraphQLAddonSchemaManagerImpl.java
@@ -56,6 +56,7 @@ public GraphQLSchema createSchema() {
                 .scalar(getDateTimeScalarType())
                 .scalar(ExtendedScalars.GraphQLBigDecimal)
                 .scalar(ExtendedScalars.GraphQLLong)
+                .scalar(ExtendedScalars.Json)
                 .build();
 
         SchemaGenerator schemaGenerator = new SchemaGenerator();