1 files changed, 11 insertions, 5 deletions

diff --git a/subprojects/store-query/src/main/java/tools/refinery/store/query/term/AbstractTerm.java b/subprojects/store-query/src/main/java/tools/refinery/store/query/term/AbstractTerm.java
index d0ae3c12..5cecc35b 100644
--- a/subprojects/store-query/src/main/java/tools/refinery/store/query/term/AbstractTerm.java
+++ b/subprojects/store-query/src/main/java/tools/refinery/store/query/term/AbstractTerm.java
@@ -6,6 +6,7 @@
 package tools.refinery.store.query.term;
 
 import tools.refinery.store.query.equality.LiteralEqualityHelper;
+import tools.refinery.store.query.equality.LiteralHashCodeHelper;
 
 import java.util.Objects;
 
@@ -17,13 +18,18 @@ public abstract class AbstractTerm<T> implements Term<T> {
         }
 
         @Override
+        public Class<T> getType() {
+                return type;
+        }
+
+        @Override
         public boolean equalsWithSubstitution(LiteralEqualityHelper helper, AnyTerm other) {
-                return getClass().equals(other.getClass()) && type.equals(other.getType());
+                return other != null && getClass() == other.getClass() && type.equals(other.getType());
         }
 
         @Override
-        public Class<T> getType() {
-                return type;
+        public int hashCodeWithSubstitution(LiteralHashCodeHelper helper) {
+                return Objects.hash(getClass(), type);
         }
 
         @Override
@@ -31,11 +37,11 @@ public abstract class AbstractTerm<T> implements Term<T> {
                 if (this == o) return true;
                 if (o == null || getClass() != o.getClass()) return false;
                 AbstractTerm<?> that = (AbstractTerm<?>) o;
-                return type.equals(that.type);
+                return equalsWithSubstitution(LiteralEqualityHelper.DEFAULT, that);
         }
 
         @Override
         public int hashCode() {
-                return Objects.hash(getClass(), type);
+                return hashCodeWithSubstitution(LiteralHashCodeHelper.DEFAULT);
         }
 }