diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/api.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/api.mustache
index 529bfc926130..361415fb7ab7 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/api.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/api.mustache
@@ -219,7 +219,23 @@ import {{packageName}}.infrastructure.Serializer
                     {{/vars}}
                     {{/isModel}}
                     {{^isModel}}
+                    {{#isMap}}
+                    {{#isExplode}}
+                    {{^isDeepObject}}
+                    // form style explodes an object into one query parameter per entry, keyed by the property name alone
+                    ({{{paramName}}} as? kotlin.collections.Map<*, *>)?.forEach { (key, value) -> put(key.toString(), listOf(value.toString())) }
+                    {{/isDeepObject}}
+                    {{#isDeepObject}}
                     put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                    {{/isDeepObject}}
+                    {{/isExplode}}
+                    {{^isExplode}}
+                    put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                    {{/isExplode}}
+                    {{/isMap}}
+                    {{^isMap}}
+                    put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                    {{/isMap}}
                     {{/isModel}}
                 }
                 {{/required}}
@@ -234,7 +250,23 @@ import {{packageName}}.infrastructure.Serializer
                     {{/vars}}
                     {{/isModel}}
                     {{^isModel}}
+                    {{#isMap}}
+                    {{#isExplode}}
+                    {{^isDeepObject}}
+                    // form style explodes an object into one query parameter per entry, keyed by the property name alone
+                    ({{{paramName}}} as? kotlin.collections.Map<*, *>)?.forEach { (key, value) -> put(key.toString(), listOf(value.toString())) }
+                    {{/isDeepObject}}
+                    {{#isDeepObject}}
+                    put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                    {{/isDeepObject}}
+                    {{/isExplode}}
+                    {{^isExplode}}
                     put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                    {{/isExplode}}
+                    {{/isMap}}
+                    {{^isMap}}
+                    put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                    {{/isMap}}
                     {{/isModel}}
                 }
                 {{/isNullable}}
@@ -247,7 +279,23 @@ import {{packageName}}.infrastructure.Serializer
                 {{/vars}}
                 {{/isModel}}
                 {{^isModel}}
+                {{#isMap}}
+                {{#isExplode}}
+                {{^isDeepObject}}
+                // form style explodes an object into one query parameter per entry, keyed by the property name alone
+                ({{{paramName}}} as? kotlin.collections.Map<*, *>)?.forEach { (key, value) -> put(key.toString(), listOf(value.toString())) }
+                {{/isDeepObject}}
+                {{#isDeepObject}}
+                put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                {{/isDeepObject}}
+                {{/isExplode}}
+                {{^isExplode}}
+                put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                {{/isExplode}}
+                {{/isMap}}
+                {{^isMap}}
                 put("{{#lambda.escapeDollar}}{{baseName}}{{/lambda.escapeDollar}}", {{#isContainer}}toMultiValue({{{paramName}}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{#isDateTime}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDateTime}}{{#isDate}}parseDateToQueryString<{{{dataType}}}>({{{paramName}}}){{/isDate}}{{#isEnum}}{{#isString}}{{{paramName}}}.value{{/isString}}{{^isString}}{{{paramName}}}.toString(){{/isString}}{{/isEnum}}{{^isEnum}}{{^isDateTime}}{{^isDate}}{{{paramName}}}.toString(){{/isDate}}{{/isDateTime}}{{/isEnum}}){{/isContainer}})
+                {{/isMap}}
                 {{/isModel}}
                 {{/isNullable}}
                 {{/required}}
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinClientCodegenApiTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinClientCodegenApiTest.java
index 04d59b0700f4..d62aae4a9618 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinClientCodegenApiTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinClientCodegenApiTest.java
@@ -229,6 +229,33 @@ public void testJvmKtorQueryParamWithTypeObject() throws IOException {
         assertFileNotContains(defaultApi.toPath(), "mapDeep?.apply {");
     }
 
+    @Test(description = "Verify an object query parameter is exploded, whether or not it declares its properties")
+    public void testExplodedObjectQueryParameterJvmOkhttp() throws IOException {
+        OpenAPI openAPI = readOpenAPI("src/test/resources/3_0/exploded-object-query-param.yaml");
+
+        KotlinClientCodegen codegen = createCodegen(ClientLibrary.JVM_OKHTTP4);
+        DefaultGenerator generator = new DefaultGenerator();
+        enableOnlyApiGeneration(generator);
+
+        List<File> files = generator.opts(createClientOptInput(openAPI, codegen)).generate();
+        File defaultApi = files.stream().filter(file -> file.getName().equals("DefaultApi.kt")).findAny().orElseThrow();
+
+        // form style with explode - the default - puts every entry on the wire under its own
+        // property name. Serializing the whole map with toString() is what used to happen.
+        assertFileContains(defaultApi.toPath(),
+                "(filter as? kotlin.collections.Map<*, *>)?.forEach { (key, value) -> put(key.toString(), listOf(value.toString())) }");
+        assertFileNotContains(defaultApi.toPath(), "put(\"filter\", listOf(filter.toString()))");
+
+        // a declared map behaves the same way
+        assertFileContains(defaultApi.toPath(),
+                "(typedFilter as? kotlin.collections.Map<*, *>)?.forEach { (key, value) -> put(key.toString(), listOf(value.toString())) }");
+
+        // deepObject and form without explode both keep a single parameter
+        assertFileContains(defaultApi.toPath(),
+                "put(\"deepFilter\", listOf(deepFilter.toString()))",
+                "put(\"flatFilter\", listOf(flatFilter.toString()))");
+    }
+
     private static void assertFileContainsLine(List<String> lines, String line) {
         Assert.assertListContains(lines, s -> s.equals(line), line);
     }
diff --git a/modules/openapi-generator/src/test/resources/3_0/exploded-object-query-param.yaml b/modules/openapi-generator/src/test/resources/3_0/exploded-object-query-param.yaml
new file mode 100644
index 000000000000..fd6fce7d5807
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/exploded-object-query-param.yaml
@@ -0,0 +1,51 @@
+openapi: 3.0.3
+info:
+  title: Exploded object query parameters
+  description: >
+    Object typed query parameters, covering the four combinations of style and explode that
+    decide how an object is put on the wire. The free-form variants matter because a
+    free-form object is flagged isMap but not isContainer.
+  version: 1.0.0
+servers:
+  - url: localhost:8080
+paths:
+  /items:
+    get:
+      operationId: listItems
+      parameters:
+        # style and explode both left out, so the form/true defaults apply: every entry
+        # becomes its own parameter, keyed by the property name alone.
+        - in: query
+          name: filter
+          schema:
+            type: object
+        # the same, but declared as a map rather than as a free-form object
+        - in: query
+          name: typedFilter
+          schema:
+            type: object
+            additionalProperties:
+              type: string
+        # deepObject nests each entry under the parameter name: deepFilter[key]=value
+        - in: query
+          name: deepFilter
+          style: deepObject
+          explode: true
+          schema:
+            type: object
+        # form without explode keeps a single parameter carrying the whole object
+        - in: query
+          name: flatFilter
+          style: form
+          explode: false
+          schema:
+            type: object
+      responses:
+        '200':
+          description: a list of items
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  type: string