diff --git a/gradle-conjure/build.gradle b/gradle-conjure/build.gradle
index eb1130996..58efb4bcb 100644
--- a/gradle-conjure/build.gradle
+++ b/gradle-conjure/build.gradle
@@ -40,6 +40,10 @@ dependencies {
     testImplementation 'org.mockito:mockito-core'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter'
     testRuntimeOnly 'org.junit.vintage:junit-vintage-engine'
+    testImplementation 'org.junit.jupiter:junit-jupiter'
+    testRuntimeOnly 'org.junit.vintage:junit-vintage-engine', {
+        because 'allows JUnit 3 and JUnit 4 tests to run'
+    }
 }
 
 gradlePlugin {
diff --git a/gradle-conjure/src/main/java/com/palantir/gradle/conjure/ConjureRunnerResource.java b/gradle-conjure/src/main/java/com/palantir/gradle/conjure/ConjureRunnerResource.java
index ff27c6030..d65d865a1 100644
--- a/gradle-conjure/src/main/java/com/palantir/gradle/conjure/ConjureRunnerResource.java
+++ b/gradle-conjure/src/main/java/com/palantir/gradle/conjure/ConjureRunnerResource.java
@@ -26,6 +26,7 @@
 import java.io.IOException;
 import java.lang.reflect.Method;
 import java.net.URLClassLoader;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Optional;
 import net.bytebuddy.ByteBuddy;
@@ -158,7 +159,7 @@ public void invoke(Project project, String failedTo, List<String> unloggedArgs,
             if (exitValue != 0) {
                 throw new RuntimeException(String.format(
                         "Failed to %s. The command '%s' failed with exit code %d. Output:\n%s",
-                        failedTo, combinedArgs, exitValue, output.toString()));
+                        failedTo, combinedArgs, exitValue, output.toString(StandardCharsets.UTF_8)));
             }
         }
     }
diff --git a/gradle-conjure/src/test/java/com/palantir/gradle/conjure/RenderGeneratorOptionsTest.java b/gradle-conjure/src/test/java/com/palantir/gradle/conjure/RenderGeneratorOptionsTest.java
index eedc46747..58771c9dc 100644
--- a/gradle-conjure/src/test/java/com/palantir/gradle/conjure/RenderGeneratorOptionsTest.java
+++ b/gradle-conjure/src/test/java/com/palantir/gradle/conjure/RenderGeneratorOptionsTest.java
@@ -21,7 +21,7 @@
 
 import com.google.common.collect.ImmutableMap;
 import com.palantir.gradle.conjure.api.GeneratorOptions;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 public class RenderGeneratorOptionsTest {
     private final GeneratorOptions generatorOptions = new GeneratorOptions();
diff --git a/gradle-conjure/src/test/java/com/palantir/gradle/conjure/ReverseEngineerJavaStartScriptTest.java b/gradle-conjure/src/test/java/com/palantir/gradle/conjure/ReverseEngineerJavaStartScriptTest.java
index 2dbe73bf3..815ea1bbf 100644
--- a/gradle-conjure/src/test/java/com/palantir/gradle/conjure/ReverseEngineerJavaStartScriptTest.java
+++ b/gradle-conjure/src/test/java/com/palantir/gradle/conjure/ReverseEngineerJavaStartScriptTest.java
@@ -20,7 +20,7 @@
 
 import java.io.File;
 import java.nio.file.Paths;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 public class ReverseEngineerJavaStartScriptTest {
 
diff --git a/versions.lock b/versions.lock
index ba624380c..236c16c54 100644
--- a/versions.lock
+++ b/versions.lock
@@ -49,7 +49,7 @@ org.hamcrest:hamcrest:2.2 (1 constraints: d20cdc04)
 org.hamcrest:hamcrest-core:1.3 (1 constraints: cc05fe3f)
 org.jetbrains:annotations:20.1.0 (1 constraints: 5f0d6b2c)
 org.junit:junit-bom:5.7.2 (11 constraints: 46b2df2f)
-org.junit.jupiter:junit-jupiter:5.7.2 (1 constraints: 15098a95)
+org.junit.jupiter:junit-jupiter:5.7.2 (2 constraints: 200ee058)
 org.junit.jupiter:junit-jupiter-api:5.7.2 (4 constraints: 87383d33)
 org.junit.jupiter:junit-jupiter-engine:5.7.2 (2 constraints: 1f17a43c)
 org.junit.jupiter:junit-jupiter-params:5.7.2 (2 constraints: 1f17a43c)
@@ -57,7 +57,7 @@ org.junit.platform:junit-platform-commons:1.7.2 (3 constraints: eb29562b)
 org.junit.platform:junit-platform-engine:1.7.2 (4 constraints: 823c4ddb)
 org.junit.platform:junit-platform-launcher:1.7.2 (2 constraints: 101b5c4a)
 org.junit.platform:junit-platform-testkit:1.7.2 (1 constraints: 11097695)
-org.junit.vintage:junit-vintage-engine:5.7.2 (1 constraints: 15098a95)
+org.junit.vintage:junit-vintage-engine:5.7.2 (2 constraints: 200ee058)
 org.mockito:mockito-core:4.2.0 (1 constraints: 08050536)
 org.objenesis:objenesis:3.2 (4 constraints: 142904bf)
 org.opentest4j:opentest4j:1.2.0 (3 constraints: c53224a1)
diff --git a/versions.props b/versions.props
index dfc90db11..5719478b4 100644
--- a/versions.props
+++ b/versions.props
@@ -9,7 +9,9 @@ junit:junit = 4.13.2
 org.apache.commons:commons-lang3 = 3.12.0
 org.assertj:* = 3.22.0
 org.immutables:value = 2.8.8
-org.mockito:mockito-core = 4.2.0
+org.junit.jupiter:* = 5.5.0
+org.junit.vintage:* = 5.5.0
+org.mockito:* = 4.2.0
 org.spockframework:* = 2.0-groovy-3.0
 com.palantir.sls-packaging:* = 7.13.0
 com.palantir.conjure.java.runtime:* = 7.22.0