diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index 4399b06e..e8d68040 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -14,6 +14,12 @@ jobs:
       matrix:
         java: [ "11", "17", "21" ]
         distribution: [ "zulu", "adopt" ]
+        okhttp: [ "okhttp5", "okhttp4" ]
+        include:
+          - okhttp: "okhttp5"
+            maven_profiles: ""
+          - okhttp: "okhttp4"
+            maven_profiles: "-P test-okhttp4"
 
     steps:
       - name: Checkout repository
@@ -31,8 +37,8 @@ jobs:
         uses: actions/cache@v4
         with:
           path: ~/.m2
-          key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
+          key: ${{ runner.os }}-m2-${{ matrix.okhttp }}-${{ hashFiles('**/pom.xml') }}
           restore-keys: ${{ runner.os }}-m2
 
-      - name: Build with Maven
-        run: mvn clean install
+      - name: Build with Maven (OkHttp ${{ matrix.okhttp }})
+        run: mvn clean install ${{ matrix.maven_profiles }}
diff --git a/pom.xml b/pom.xml
index b088bcc8..284df292 100644
--- a/pom.xml
+++ b/pom.xml
@@ -48,13 +48,17 @@
     <slf4j.version>1.7.30</slf4j.version>
     <maven.checkstyle.version>3.4.0</maven.checkstyle.version>
     <junit.jupiter.version>5.14.0</junit.jupiter.version>
+    <!-- OkHttp dependency coordinates — overridden by the test-okhttp4 profile -->
+    <okhttp.artifactId>okhttp-jvm</okhttp.artifactId>
+    <okhttp.version>5.0.0</okhttp.version>
+    <okhttp.mockwebserver.version>5.0.0</okhttp.mockwebserver.version>
   </properties>
 
   <dependencies>
     <dependency>
       <groupId>com.squareup.okhttp3</groupId>
-      <artifactId>okhttp</artifactId>
-      <version>4.12.0</version>
+      <artifactId>${okhttp.artifactId}</artifactId>
+      <version>${okhttp.version}</version>
     </dependency>
     <dependency>
       <groupId>com.jayway.jsonpath</groupId>
@@ -157,7 +161,7 @@
     <dependency>
       <groupId>com.squareup.okhttp3</groupId>
       <artifactId>mockwebserver</artifactId>
-      <version>3.10.0</version>
+      <version>${okhttp.mockwebserver.version}</version>
       <scope>test</scope>
     </dependency>
     <dependency>
@@ -173,9 +177,9 @@
         <version>1.14.17</version>
     </dependency>
     <dependency>
-      <groupId>com.github.gmazzo</groupId>
-      <artifactId>okhttp-mock</artifactId>
-      <version>1.4.1</version>
+      <groupId>com.github.gmazzo.okhttp.mock</groupId>
+      <artifactId>mock-client</artifactId>
+      <version>2.0.0</version>
       <scope>test</scope>
     </dependency>
   </dependencies>
@@ -368,5 +372,17 @@
         </plugins>
       </build>
     </profile>
+    <profile>
+      <!--
+        Run the test suite against OkHttp 4.x to verify backward compatibility.
+        Activate with: mvn test -P test-okhttp4
+      -->
+      <id>test-okhttp4</id>
+      <properties>
+        <okhttp.artifactId>okhttp</okhttp.artifactId>
+        <okhttp.version>4.12.0</okhttp.version>
+        <okhttp.mockwebserver.version>4.12.0</okhttp.mockwebserver.version>
+      </properties>
+    </profile>
   </profiles>
 </project>
diff --git a/src/main/java/com/flagsmith/FlagsmithApiWrapper.java b/src/main/java/com/flagsmith/FlagsmithApiWrapper.java
index c1478f92..bb7f06af 100644
--- a/src/main/java/com/flagsmith/FlagsmithApiWrapper.java
+++ b/src/main/java/com/flagsmith/FlagsmithApiWrapper.java
@@ -201,7 +201,7 @@ public Flags identifyUserWithTraits(
       node.putPOJO("traits", traits);
     }
 
-    MediaType json = MediaType.parse("application/json; charset=utf-8");
+    MediaType json = MediaType.get("application/json; charset=utf-8");
     RequestBody body = RequestBody.create(node.toString(), json);
 
     HttpUrl url = defaultConfig.getIdentitiesUri();
diff --git a/src/main/java/com/flagsmith/config/FlagsmithConfig.java b/src/main/java/com/flagsmith/config/FlagsmithConfig.java
index e2ea1a8a..ffb7357f 100644
--- a/src/main/java/com/flagsmith/config/FlagsmithConfig.java
+++ b/src/main/java/com/flagsmith/config/FlagsmithConfig.java
@@ -28,7 +28,7 @@ public final class FlagsmithConfig {
   private static final int DEFAULT_READ_TIMEOUT_MILLIS = 5000;
   private static final int DEFAULT_ENVIRONMENT_REFRESH_SECONDS = 60;
   private static final HttpUrl DEFAULT_BASE_URI = HttpUrl
-      .parse("https://edge.api.flagsmith.com/api/v1/");
+      .get("https://edge.api.flagsmith.com/api/v1/");
   private final HttpUrl flagsUri;
   private final HttpUrl identitiesUri;
   private final HttpUrl traitsUri;
@@ -129,7 +129,7 @@ private Builder() {
      */
     public Builder baseUri(String baseUri) {
       if (baseUri != null) {
-        this.baseUri = HttpUrl.parse(baseUri);
+        this.baseUri = HttpUrl.get(baseUri);
       }
       return this;
     }
diff --git a/src/main/java/com/flagsmith/threads/AnalyticsProcessor.java b/src/main/java/com/flagsmith/threads/AnalyticsProcessor.java
index 58ddf412..da631f56 100644
--- a/src/main/java/com/flagsmith/threads/AnalyticsProcessor.java
+++ b/src/main/java/com/flagsmith/threads/AnalyticsProcessor.java
@@ -132,8 +132,8 @@ public void flush() {
         return;
       }
 
-      MediaType json = MediaType.parse("application/json; charset=utf-8");
-      RequestBody body = RequestBody.create(json, response);
+      MediaType json = MediaType.get("application/json; charset=utf-8");
+      RequestBody body = RequestBody.create(response, json);
 
       Request request = api.newPostRequest(getAnalyticsUrl(), body);
 
diff --git a/src/test/java/com/flagsmith/FlagsmithApiWrapperTest.java b/src/test/java/com/flagsmith/FlagsmithApiWrapperTest.java
index ad4df9fb..14caf72c 100644
--- a/src/test/java/com/flagsmith/FlagsmithApiWrapperTest.java
+++ b/src/test/java/com/flagsmith/FlagsmithApiWrapperTest.java
@@ -38,7 +38,6 @@
 import okhttp3.Response;
 import okhttp3.ResponseBody;
 import okhttp3.mock.MockInterceptor;
-import org.bouncycastle.ocsp.Req;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;