diff --git a/modules/openapi-generator/src/main/resources/rust/reqwest-trait/api.mustache b/modules/openapi-generator/src/main/resources/rust/reqwest-trait/api.mustache
index cf16c0fc24b2..093832d31435 100644
--- a/modules/openapi-generator/src/main/resources/rust/reqwest-trait/api.mustache
+++ b/modules/openapi-generator/src/main/resources/rust/reqwest-trait/api.mustache
@@ -205,12 +205,11 @@ impl {{classname}} for {{classname}}Client {
         }
         {{/isModel}}
         {{#isMap}}
+        {{!-- one route for the HashMap and the free-form serde_json::Value shape alike,
+              and the same deepObject wire format the non-explode branch produces --}}
         if let Some(ref param_value) = {{{paramName}}} {
-            let mut query_params = Vec::with_capacity(param_value.len());
-            for (key, value) in param_value.iter() {
-                query_params.push((key.to_string(), serde_json::to_string(value)?));
-            }
-            local_var_req_builder = local_var_req_builder.query(&query_params);
+            let params = crate::apis::parse_deep_object("{{{baseName}}}", &serde_json::to_value(param_value)?);
+            local_var_req_builder = local_var_req_builder.query(&params);
         }
         {{/isMap}}
         {{/isExplode}}
@@ -256,11 +255,10 @@ impl {{classname}} for {{classname}}Client {
             local_var_req_builder = local_var_req_builder.query(&param_value);
             {{/isModel}}
             {{#isMap}}
-            let mut query_params = Vec::with_capacity(param_value.len());
-            for (key, value) in param_value.iter() {
-                query_params.push((key.to_string(), serde_json::to_string(value)?));
-            }
-            local_var_req_builder = local_var_req_builder.query(&query_params);
+            {{!-- one route for the HashMap and the free-form serde_json::Value shape alike,
+                  and the same deepObject wire format the non-explode branch produces --}}
+            let params = crate::apis::parse_deep_object("{{{baseName}}}", &serde_json::to_value(param_value)?);
+            local_var_req_builder = local_var_req_builder.query(&params);
             {{/isMap}}
             {{/isExplode}}
             {{/isDeepObject}}
diff --git a/modules/openapi-generator/src/main/resources/rust/reqwest/api.mustache b/modules/openapi-generator/src/main/resources/rust/reqwest/api.mustache
index 5224b0c4d9b5..8b363e700593 100644
--- a/modules/openapi-generator/src/main/resources/rust/reqwest/api.mustache
+++ b/modules/openapi-generator/src/main/resources/rust/reqwest/api.mustache
@@ -180,11 +180,10 @@ pub {{#supportAsync}}async {{/supportAsync}}fn {{{operationId}}}(configuration:
         req_builder = req_builder.query(&param_value);
         {{/isModel}}
         {{#isMap}}
-        let mut query_params = Vec::with_capacity(param_value.len());
-        for (key, value) in param_value.iter() {
-            query_params.push((key.to_string(), serde_json::to_string(value)?));
-        }
-        req_builder = req_builder.query(&query_params);
+        {{!-- one route for the HashMap and the free-form serde_json::Value shape alike,
+              and the same deepObject wire format the non-explode branch produces --}}
+        let params = crate::apis::parse_deep_object("{{{baseName}}}", &serde_json::to_value(param_value)?);
+        req_builder = req_builder.query(&params);
         {{/isMap}}
         {{/isExplode}}
     };
@@ -251,11 +250,10 @@ pub {{#supportAsync}}async {{/supportAsync}}fn {{{operationId}}}(configuration:
         req_builder = req_builder.query(&param_value);
         {{/isModel}}
         {{#isMap}}
-        let mut query_params = Vec::with_capacity(param_value.len());
-        for (key, value) in param_value.iter() {
-            query_params.push((key.to_string(), serde_json::to_string(value)?));
-        }
-        req_builder = req_builder.query(&query_params);
+        {{!-- one route for the HashMap and the free-form serde_json::Value shape alike,
+              and the same deepObject wire format the non-explode branch produces --}}
+        let params = crate::apis::parse_deep_object("{{{baseName}}}", &serde_json::to_value(param_value)?);
+        req_builder = req_builder.query(&params);
         {{/isMap}}
         {{/isExplode}}
         {{/isDeepObject}}
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/rust/RustClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/rust/RustClientCodegenTest.java
index d4bc7c1845ec..bebb54132710 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/rust/RustClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/rust/RustClientCodegenTest.java
@@ -293,6 +293,36 @@ public void testIntegerPropertyEnum() throws IOException {
         TestUtils.assertFileNotContains(outputPath, linearize("#[serde(rename = \"0\")]"));
     }
 
+    @Test
+    public void testDeepObjectFreeFormQueryParamCompiles() throws IOException {
+        // the exploded deepObject branch walked every map-flagged parameter with
+        // .len()/.iter() - fine for a HashMap-typed map, but a bare free-form object is a
+        // serde_json::Value, which has neither, so the generated crate did not compile;
+        // both shapes now take parse_deep_object, the route the non-explode branch already
+        // uses, which also yields the deepObject wire format the style asks for
+        for (String library : new String[] {"reqwest", "reqwest-trait"}) {
+            Path target = Files.createTempDirectory("test");
+            target.toFile().deleteOnExit();
+            final CodegenConfigurator configurator = new CodegenConfigurator()
+                    .setGeneratorName("rust")
+                    .setLibrary(library)
+                    .setInputSpec("src/test/resources/3_0/rust/deep-object-free-form-query-param.yaml")
+                    .setSkipOverwrite(false)
+                    .setOutputDir(target.toAbsolutePath().toString().replace("\\", "/"));
+            List<File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate();
+            files.forEach(File::deleteOnExit);
+            Path outputPath = Path.of(target.toString(), "/src/apis/default_api.rs");
+            TestUtils.assertFileExists(outputPath);
+            // the optional typed map, the optional free-form object, and the
+            // required-nullable map all route through parse_deep_object
+            TestUtils.assertFileContains(outputPath, "crate::apis::parse_deep_object(\"filter\"");
+            TestUtils.assertFileContains(outputPath, "crate::apis::parse_deep_object(\"extra\"");
+            TestUtils.assertFileContains(outputPath, "crate::apis::parse_deep_object(\"scope\"");
+            TestUtils.assertFileNotContains(outputPath, "param_value.len()");
+            TestUtils.assertFileNotContains(outputPath, "param_value.iter()");
+        }
+    }
+
     @Test
     public void testArrayWithObjectEnumValues() throws IOException {
         Path target = Files.createTempDirectory("test");
diff --git a/modules/openapi-generator/src/test/resources/3_0/rust/deep-object-free-form-query-param.yaml b/modules/openapi-generator/src/test/resources/3_0/rust/deep-object-free-form-query-param.yaml
new file mode 100644
index 000000000000..5780ef2bf2da
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/rust/deep-object-free-form-query-param.yaml
@@ -0,0 +1,35 @@
+openapi: 3.0.3
+info:
+  title: deep object params
+  version: 1.0.0
+paths:
+  /items:
+    get:
+      operationId: listItems
+      parameters:
+        - name: filter
+          in: query
+          style: deepObject
+          explode: true
+          schema:
+            type: object
+            additionalProperties: true
+        - name: extra
+          in: query
+          style: deepObject
+          explode: true
+          schema:
+            type: object
+        - name: scope
+          in: query
+          required: true
+          style: deepObject
+          explode: true
+          schema:
+            type: object
+            nullable: true
+            additionalProperties:
+              type: string
+      responses:
+        '200':
+          description: ok