diff --git a/build.gradle.kts b/build.gradle.kts
index a09baba..a353129 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -88,7 +88,8 @@ subprojects {
         testImplementation("org.hamcrest:hamcrest-core:$hamcrestVersion")
         testImplementation("com.google.guava:guava-testlib:$guavaVersion")
         testImplementation("org.apache.logging.log4j:log4j-core:$log4jVersion")
-        testImplementation("org.apache.logging.log4j:log4j-slf4j2-impl:$log4jVersion")
+        // An old v1.x SLF4J impl as required by mbknor-jackson-jsonschema
+        testRuntimeOnly("org.apache.logging.log4j:log4j-slf4j-impl:$log4jVersion")
         testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine:$junitVersion")
     }
 
diff --git a/generator/build.gradle.kts b/generator/build.gradle.kts
index 4178eae..c42336c 100644
--- a/generator/build.gradle.kts
+++ b/generator/build.gradle.kts
@@ -37,7 +37,8 @@ dependencies {
     implementation("com.kjetland:mbknor-jackson-jsonschema_2.13:$jsonSchemaVersion")
     implementation("io.github.classgraph:classgraph:$classGraphVersion")
     implementation("org.apache.logging.log4j:log4j-core:$log4jVersion")
-    runtimeOnly("org.apache.logging.log4j:log4j-slf4j-impl:$log4jVersion")
+    // An old v1.x SLF4J impl as required by mbknor-jackson-jsonschema
+    implementation("org.apache.logging.log4j:log4j-slf4j-impl:$log4jVersion")
 
     testImplementation(project(":test-types"))
 }