diff --git a/optaplanner-core/src/main/java/org/optaplanner/core/impl/domain/solution/AbstractSolution.java b/optaplanner-core/src/main/java/org/optaplanner/core/impl/domain/solution/AbstractSolution.java
index 0c90a4676b..7d931836f2 100644
--- a/optaplanner-core/src/main/java/org/optaplanner/core/impl/domain/solution/AbstractSolution.java
+++ b/optaplanner-core/src/main/java/org/optaplanner/core/impl/domain/solution/AbstractSolution.java
@@ -21,6 +21,7 @@
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.List;
 import java.util.Map;
 
 import org.optaplanner.core.api.domain.solution.PlanningEntityCollectionProperty;
@@ -50,21 +51,25 @@ public void setScore(S score) {
     }
 
     /**
-     * Convenience method for tests.
-     *
-     * @return All entities from anywhere in this class' hierarchy.
+     * @return a list with every problem fact that is in a field of this class
+     * (directly or indirectly as an element of a {@link Collection} or {@link Map} field)
      */
     @ProblemFactCollectionProperty
-    protected Collection<?> getProblemFacts() {
-        Class<? extends AbstractSolution> instanceClass = getClass();
-        return getProblemFactsFromClass(instanceClass);
+    protected List<Object> getProblemFactList() {
+        List<Object> factList = new ArrayList<Object>();
+        addProblemFactsFromClass(factList, getClass());
+        return factList;
     }
 
-    private Collection<Object> getProblemFactsFromClass(Class<?> instanceClass) {
-        Collection<Object> factList = new ArrayList<>();
+    /**
+     * Adds to an existing to {@link List} to avoid copying the entire list with {@link List#addAll(Collection)}.
+     * @param factList never null
+     * @param instanceClass never null
+     */
+    private void addProblemFactsFromClass(List<Object> factList, Class<?> instanceClass) {
         if (instanceClass.equals(AbstractSolution.class)) {
             // The field score should not be included
-            return factList;
+            return;
         }
         for (Field field : instanceClass.getDeclaredFields()) {
             field.setAccessible(true);
@@ -91,9 +96,8 @@ private Collection<Object> getProblemFactsFromClass(Class<?> instanceClass) {
         }
         Class<?> superclass = instanceClass.getSuperclass();
         if (superclass != null) {
-            factList.addAll(getProblemFactsFromClass(superclass));
+            addProblemFactsFromClass(factList, superclass);
         }
-        return factList;
     }
 
     private boolean isFieldAPlanningEntityPropertyOrPlanningEntityCollectionProperty(Field field,
diff --git a/optaplanner-core/src/main/java/org/optaplanner/core/impl/domain/solution/mutation/MutationCounter.java b/optaplanner-core/src/main/java/org/optaplanner/core/impl/domain/solution/mutation/MutationCounter.java
index 47b3c0c10b..383794b903 100644
--- a/optaplanner-core/src/main/java/org/optaplanner/core/impl/domain/solution/mutation/MutationCounter.java
+++ b/optaplanner-core/src/main/java/org/optaplanner/core/impl/domain/solution/mutation/MutationCounter.java
@@ -49,7 +49,7 @@ public int countMutations(Solution_ a, Solution_ b) {
             for (Iterator aIt = aEntities.iterator(), bIt = bEntities.iterator(); aIt.hasNext() && bIt.hasNext(); ) {
                 Object aEntity =  aIt.next();
                 Object bEntity =  bIt.next();
-                for (GenuineVariableDescriptor variableDescriptor : entityDescriptor.getGenuineVariableDescriptors()) {
+                for (GenuineVariableDescriptor<Solution_> variableDescriptor : entityDescriptor.getGenuineVariableDescriptors()) {
                     // TODO broken if the value is an entity, because then it's never the same
                     // But we don't want to depend on value/entity equals() => use surrogate entity id's to compare
                     // https://issues.jboss.org/browse/PLANNER-170
@@ -70,4 +70,5 @@ public int countMutations(Solution_ a, Solution_ b) {
     public String toString() {
         return "MutationCounter(" + solutionDescriptor + ")";
     }
+
 }
diff --git a/optaplanner-core/src/test/java/org/optaplanner/core/impl/domain/solution/AbstractSolutionTest.java b/optaplanner-core/src/test/java/org/optaplanner/core/impl/domain/solution/AbstractSolutionTest.java
index 94640e2dad..0514dbf344 100644
--- a/optaplanner-core/src/test/java/org/optaplanner/core/impl/domain/solution/AbstractSolutionTest.java
+++ b/optaplanner-core/src/test/java/org/optaplanner/core/impl/domain/solution/AbstractSolutionTest.java
@@ -16,7 +16,6 @@
 
 package org.optaplanner.core.impl.domain.solution;
 
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
@@ -63,7 +62,7 @@ public void getProblemFacts() {
         solution.setSingleEntity(singleEntity);
         SimpleScore score = SimpleScore.valueOf(-10);
         solution.setScore(score);
-        assertCollectionContainsExactly((Collection<Object>) solution.getProblemFacts(), singleValue, v1, v2, v3);
+        assertCollectionContainsExactly(solution.getProblemFactList(), singleValue, v1, v2, v3);
     }
 
     @Test
@@ -78,7 +77,7 @@ public void getProblemFactsWithNullField() {
         solution.setEntityList(null);
         solution.setSingleEntity(null);
         solution.setScore(null);
-        assertCollectionContainsExactly((Collection<Object>) solution.getProblemFacts(), v1, v2, v3);
+        assertCollectionContainsExactly(solution.getProblemFactList(), v1, v2, v3);
     }
 
     public static class TestdataAbstractSolutionBasedSolution extends AbstractSolution<SimpleScore> {
diff --git a/optaplanner-core/src/test/java/org/optaplanner/core/impl/testdata/domain/extended/abstractsolution/TestdataExtendedAbstractSolution.java b/optaplanner-core/src/test/java/org/optaplanner/core/impl/testdata/domain/extended/abstractsolution/TestdataExtendedAbstractSolution.java
index 7e0d2ccc18..591e25cc3a 100644
--- a/optaplanner-core/src/test/java/org/optaplanner/core/impl/testdata/domain/extended/abstractsolution/TestdataExtendedAbstractSolution.java
+++ b/optaplanner-core/src/test/java/org/optaplanner/core/impl/testdata/domain/extended/abstractsolution/TestdataExtendedAbstractSolution.java
@@ -19,11 +19,14 @@
 import java.util.List;
 
 import org.optaplanner.core.api.domain.solution.PlanningEntityCollectionProperty;
+import org.optaplanner.core.api.domain.solution.drools.ProblemFactCollectionProperty;
 import org.optaplanner.core.api.domain.solution.drools.ProblemFactProperty;
 import org.optaplanner.core.api.domain.solution.PlanningSolution;
+import org.optaplanner.core.api.domain.valuerange.ValueRangeProvider;
 import org.optaplanner.core.impl.domain.solution.AbstractSolution;
 import org.optaplanner.core.impl.domain.solution.descriptor.SolutionDescriptor;
 import org.optaplanner.core.impl.testdata.domain.TestdataEntity;
+import org.optaplanner.core.impl.testdata.domain.TestdataValue;
 
 @PlanningSolution
 public class TestdataExtendedAbstractSolution extends AbstractSolution {
@@ -32,6 +35,7 @@ public static SolutionDescriptor buildSolutionDescriptor() {
         return SolutionDescriptor.buildSolutionDescriptor(TestdataExtendedAbstractSolution.class, TestdataEntity.class);
     }
 
+    private List<TestdataValue> valueList;
     private Object extraObject;
 
     private List<TestdataEntity> entityList;
@@ -40,6 +44,16 @@ public TestdataExtendedAbstractSolution(String code) {
         super();
     }
 
+    @ValueRangeProvider(id = "valueRange")
+    @ProblemFactCollectionProperty
+    public List<TestdataValue> getValueList() {
+        return valueList;
+    }
+
+    public void setValueList(List<TestdataValue> valueList) {
+        this.valueList = valueList;
+    }
+
     @ProblemFactProperty
     public Object getExtraObject() {
         return extraObject;