diff --git a/extensions/smallrye-jwt-build/runtime/src/main/java/io/quarkus/smallrye/jwt/build/runtime/graalvm/Substitutions.java b/extensions/smallrye-jwt-build/runtime/src/main/java/io/quarkus/smallrye/jwt/build/runtime/graalvm/Substitutions.java
index 4d09817c95dc1..c7e868d0b0a74 100644
--- a/extensions/smallrye-jwt-build/runtime/src/main/java/io/quarkus/smallrye/jwt/build/runtime/graalvm/Substitutions.java
+++ b/extensions/smallrye-jwt-build/runtime/src/main/java/io/quarkus/smallrye/jwt/build/runtime/graalvm/Substitutions.java
@@ -5,25 +5,34 @@
 import com.oracle.svm.core.annotate.Substitute;
 import com.oracle.svm.core.annotate.TargetClass;
 
-@TargetClass(className = "org.jose4j.jwk.OctetKeyPairJsonWebKey", onlyWith = JavaVersionLessThan17.class)
+@TargetClass(className = "org.jose4j.jwk.OctetKeyPairJsonWebKey", onlyWith = JavaVersionLessThan17andOctetKeyPairOnClasspath.class)
 final class Target_org_jose4j_jwk_OctetKeyPairJsonWebKey {
     @Substitute
     public Target_org_jose4j_jwk_OctetKeyPairJsonWebKey(java.security.PublicKey publicKey) {
+        throw new UnsupportedOperationException(
+                "OctetKeyPairJsonWebKey depends on EdECPrivateKeySpec which is not available in Java < 15");
     }
 
     @Substitute
     Target_org_jose4j_jwk_OctetKeyPairUtil subtypeKeyUtil() {
-        return null;
+        throw new UnsupportedOperationException(
+                "OctetKeyPairJsonWebKey depends on EdECPrivateKeySpec which is not available in Java < 15");
     }
 }
 
-@TargetClass(className = "org.jose4j.keys.OctetKeyPairUtil", onlyWith = JavaVersionLessThan17.class)
+@TargetClass(className = "org.jose4j.keys.OctetKeyPairUtil", onlyWith = JavaVersionLessThan17andOctetKeyPairOnClasspath.class)
 final class Target_org_jose4j_jwk_OctetKeyPairUtil {
 }
 
-class JavaVersionLessThan17 implements BooleanSupplier {
+class JavaVersionLessThan17andOctetKeyPairOnClasspath implements BooleanSupplier {
     @Override
     public boolean getAsBoolean() {
-        return Runtime.version().version().get(0) < 17;
+        try {
+            Class.forName("org.jose4j.jwk.OctetKeyPairJsonWebKey");
+            Class.forName("org.jose4j.jwk.OctetKeyPairUtil");
+            return Runtime.version().version().get(0) < 17;
+        } catch (ClassNotFoundException e) {
+            return false;
+        }
     }
 }