diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index fb5760ba383..0c913215904 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -241,6 +241,8 @@ Bug Fixes
 * SOLR-13727: Fixed V2Requests - HttpSolrClient replaced first instance of "/solr" with "/api" which
   caused a change in host names starting with "solr".  (Megan Carey via yonik)
 
+* SOLR-13180: Fix ClassCastException in Json Request API (Johannes Kloos, Jan Høydahl, Munendra S N)
+
 Other Changes
 ----------------------
 
diff --git a/solr/core/src/java/org/apache/solr/request/json/ObjectUtil.java b/solr/core/src/java/org/apache/solr/request/json/ObjectUtil.java
index fc677812388..b9c73bc4bc3 100644
--- a/solr/core/src/java/org/apache/solr/request/json/ObjectUtil.java
+++ b/solr/core/src/java/org/apache/solr/request/json/ObjectUtil.java
@@ -22,6 +22,8 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.apache.solr.common.SolrException;
+
 public class ObjectUtil {
 
   public static class ConflictHandler {
@@ -103,10 +105,14 @@ public class ObjectUtil {
         // OK, now we need to merge values
         handler.handleConflict(outer, path, key, val, existingVal);
       }
-    } else {
+    } else if (val instanceof Map) {
       // merging at top level...
       Map<String,Object> newMap = (Map<String,Object>)val;
       handler.mergeMap(outer, newMap, path);
+    } else {
+      // todo: find a way to return query param in error message
+      throw new SolrException(SolrException.ErrorCode.BAD_REQUEST,
+          "Expected JSON Object but got " + val.getClass().getSimpleName() + "=" + val);
     }
   }
 
diff --git a/solr/core/src/java/org/apache/solr/request/json/RequestUtil.java b/solr/core/src/java/org/apache/solr/request/json/RequestUtil.java
index 6370bef7dc4..e1ddfcfb549 100644
--- a/solr/core/src/java/org/apache/solr/request/json/RequestUtil.java
+++ b/solr/core/src/java/org/apache/solr/request/json/RequestUtil.java
@@ -270,6 +270,8 @@ public class RequestUtil {
           ObjectUtil.mergeObjects(json, path, o, handler);
         }
       }
+    } catch (JSONParser.ParseException e ) {
+      throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, e);
     } catch (IOException e) {
       // impossible
     }
diff --git a/solr/core/src/test/org/apache/solr/search/json/TestJsonRequest.java b/solr/core/src/test/org/apache/solr/search/json/TestJsonRequest.java
index bcc936d5378..9f34db06c90 100644
--- a/solr/core/src/test/org/apache/solr/search/json/TestJsonRequest.java
+++ b/solr/core/src/test/org/apache/solr/search/json/TestJsonRequest.java
@@ -19,12 +19,13 @@ package org.apache.solr.search.json;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.solr.JSONTestUtil;
 import org.apache.solr.SolrTestCaseHS;
-
+import org.apache.solr.common.SolrException;
 import org.apache.solr.common.params.CommonParams;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
+
 @LuceneTestCase.SuppressCodecs({"Lucene3x","Lucene40","Lucene41","Lucene42","Lucene45","Appending"})
 public class TestJsonRequest extends SolrTestCaseHS {
 
@@ -79,6 +80,15 @@ public class TestJsonRequest extends SolrTestCaseHS {
         , "response/numFound==2"
     );
 
+    // invalid value
+    SolrException ex = expectThrows(SolrException.class, () -> client.testJQ(params("q", "*:*", "json", "5")));
+    assertEquals(SolrException.ErrorCode.BAD_REQUEST.code, ex.code());
+
+    // this is to verify other json params are not affected
+    client.testJQ( params("q", "cat_s:A", "json.limit", "1"),
+        "response/numFound==2"
+    );
+
     // test multiple json params
     client.testJQ( params("json","{query:'cat_s:A'}", "json","{filter:'where_s:NY'}")
         , "response/numFound==1"