diff --git a/CedarJava/build.gradle b/CedarJava/build.gradle
index 61c7311..719e1fa 100644
--- a/CedarJava/build.gradle
+++ b/CedarJava/build.gradle
@@ -227,6 +227,16 @@ test {
     }
 }
 
+compileTestJava {
+    sourceCompatibility = "17"
+    targetCompatibility = "17"
+}
+
+compileJava {
+    sourceCompatibility = "1.8"
+    targetCompatibility = "1.8"
+}
+
 tasks.named('build') {
     dependsOn('uberJar')
 }
diff --git a/CedarJava/src/main/java/com/cedarpolicy/model/SourceLocation.java b/CedarJava/src/main/java/com/cedarpolicy/model/SourceLocation.java
index 2947c28..48c6ff8 100644
--- a/CedarJava/src/main/java/com/cedarpolicy/model/SourceLocation.java
+++ b/CedarJava/src/main/java/com/cedarpolicy/model/SourceLocation.java
@@ -39,7 +39,7 @@ public boolean equals(final Object lhs) {
             return false;
         }
 
-        final var sl = (SourceLocation) lhs;
+        final SourceLocation sl = (SourceLocation) lhs;
         return this.start == sl.start && this.end == sl.end;
     }
 
diff --git a/CedarJava/src/main/java/com/cedarpolicy/model/policy/Policy.java b/CedarJava/src/main/java/com/cedarpolicy/model/policy/Policy.java
index 3fdac94..2f58c76 100644
--- a/CedarJava/src/main/java/com/cedarpolicy/model/policy/Policy.java
+++ b/CedarJava/src/main/java/com/cedarpolicy/model/policy/Policy.java
@@ -86,17 +86,17 @@ public String toJson() throws InternalException, NullPointerException {
     }
 
     public static Policy fromJson(String policyId, String policyJson) throws InternalException, NullPointerException {
-        var policyText = fromJsonJni(policyJson);
+        String policyText = fromJsonJni(policyJson);
         return new Policy(policyText, policyId);
     }
 
     public static Policy parseStaticPolicy(String policyStr) throws InternalException, NullPointerException {
-        var policyText = parsePolicyJni(policyStr);
+        String policyText = parsePolicyJni(policyStr);
         return new Policy(policyText, null);
     }
 
     public static Policy parsePolicyTemplate(String templateStr)  throws InternalException, NullPointerException {
-        var templateText = parsePolicyTemplateJni(templateStr);
+        String templateText = parsePolicyTemplateJni(templateStr);
         return new Policy(templateText, null);
     }
 
diff --git a/CedarJava/src/main/java/com/cedarpolicy/serializer/JsonEUID.java b/CedarJava/src/main/java/com/cedarpolicy/serializer/JsonEUID.java
index 0179ac2..194beb9 100644
--- a/CedarJava/src/main/java/com/cedarpolicy/serializer/JsonEUID.java
+++ b/CedarJava/src/main/java/com/cedarpolicy/serializer/JsonEUID.java
@@ -22,6 +22,7 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.cedarpolicy.value.EntityUID;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import java.util.Optional;
 
 /** Represent JSON format of Entity Unique Identifier. */
 public class JsonEUID {
@@ -36,7 +37,7 @@ public class JsonEUID {
     @Override
     public String toString() {
         try {
-            var mapper = new ObjectMapper();
+            ObjectMapper mapper = new ObjectMapper();
             return mapper.writeValueAsString(this);
         } catch (JsonProcessingException e) {
             throw new RuntimeException("Internal invariant violated, json encoding failed: " + e.toString());
@@ -55,9 +56,9 @@ public JsonEUID(String type, String id) {
 
     @SuppressFBWarnings("CT_CONSTRUCTOR_THROW")
     public JsonEUID(String src) throws InvalidEUIDException {
-        var o = EntityUID.parse(src);
+        Optional<EntityUID> o = EntityUID.parse(src);
         if (o.isPresent()) {
-            var x = o.get().asJson();
+            JsonEUID x = o.get().asJson();
             this.type = x.type;
             this.id = x.id;
         } else {
diff --git a/CedarJava/src/main/java/com/cedarpolicy/serializer/ValueDeserializer.java b/CedarJava/src/main/java/com/cedarpolicy/serializer/ValueDeserializer.java
index ca9e748..b2cf656 100644
--- a/CedarJava/src/main/java/com/cedarpolicy/serializer/ValueDeserializer.java
+++ b/CedarJava/src/main/java/com/cedarpolicy/serializer/ValueDeserializer.java
@@ -37,6 +37,7 @@
 import java.io.IOException;
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Optional;
 
 /** Deserialize Json to Value. This is mostly an implementation detail, but you may need to modify it if you extend the
  * `Value` class. */
@@ -95,12 +96,12 @@ public Value deserialize(JsonParser parser, DeserializationContext context) thro
                                     numFields++;
                                 }
                                 if (numFields == 2) {
-                                    var id = new EntityIdentifier(val.get("id").textValue());
-                                    var type = EntityTypeName.parse(val.get("type").textValue());
+                                    EntityIdentifier id = new EntityIdentifier(val.get("id").textValue());
+                                    Optional<EntityTypeName> type = EntityTypeName.parse(val.get("type").textValue());
                                     if (type.isPresent()) {
                                         return new EntityUID(type.get(), id);
                                     } else {
-                                        var msg = "Invalid Entity Type" + val.get("type").textValue();
+                                        String msg = "Invalid Entity Type" + val.get("type").textValue();
                                         throw new InvalidValueDeserializationException(parser, msg, node.asToken(), Map.class);
                                     }
                                 }
diff --git a/CedarJava/src/main/java/com/cedarpolicy/value/EntityIdentifier.java b/CedarJava/src/main/java/com/cedarpolicy/value/EntityIdentifier.java
index 7d88e02..dcfbdfc 100644
--- a/CedarJava/src/main/java/com/cedarpolicy/value/EntityIdentifier.java
+++ b/CedarJava/src/main/java/com/cedarpolicy/value/EntityIdentifier.java
@@ -59,7 +59,7 @@ public boolean equals(Object o) {
             return false;
         } else {
             try {
-                var rhs = (EntityIdentifier) o;
+                EntityIdentifier rhs = (EntityIdentifier) o;
                 return this.id.equals(rhs.id);
             } catch (ClassCastException e) {
                 return false;
diff --git a/CedarJava/src/main/java/com/cedarpolicy/value/EntityTypeName.java b/CedarJava/src/main/java/com/cedarpolicy/value/EntityTypeName.java
index e0f4c30..70bb011 100644
--- a/CedarJava/src/main/java/com/cedarpolicy/value/EntityTypeName.java
+++ b/CedarJava/src/main/java/com/cedarpolicy/value/EntityTypeName.java
@@ -114,7 +114,7 @@ public boolean equals(Object rhs) {
             return true;
         }
         try {
-            var rhsTypename = (EntityTypeName) rhs;
+            EntityTypeName rhsTypename = (EntityTypeName) rhs;
             return basename.equals(rhsTypename.basename) && namespace.equals(rhsTypename.namespace);
         } catch (ClassCastException e) {
             return false;
diff --git a/CedarJava/src/main/java/com/cedarpolicy/value/EntityUID.java b/CedarJava/src/main/java/com/cedarpolicy/value/EntityUID.java
index 3fea1ce..7ce53b0 100644
--- a/CedarJava/src/main/java/com/cedarpolicy/value/EntityUID.java
+++ b/CedarJava/src/main/java/com/cedarpolicy/value/EntityUID.java
@@ -87,7 +87,7 @@ public boolean equals(Object o) {
             return true;
         } else {
             try {
-                var rhs = (EntityUID) o;
+                EntityUID rhs = (EntityUID) o;
                 return this.type.equals(rhs.type) && this.id.equals(rhs.id);
             } catch (ClassCastException e) {
                 return false;
@@ -122,4 +122,3 @@ public static Optional<EntityUID> parseFromJson(JsonEUID euid) {
     private static native String getEUIDRepr(EntityTypeName type, EntityIdentifier id);
 
 }
-