diff --git a/src/main/java/org/veupathdb/service/eda/common/model/EntityDef.java b/src/main/java/org/veupathdb/service/eda/common/model/EntityDef.java
index 871d18e0..38d60024 100644
--- a/src/main/java/org/veupathdb/service/eda/common/model/EntityDef.java
+++ b/src/main/java/org/veupathdb/service/eda/common/model/EntityDef.java
@@ -158,7 +158,7 @@ public String toString() {
   }
 
   public void addVariable(VariableDef variable) {
-    addIfUnique(_categories, EntityChildUniquenessKey::fromVar, variable);
+    addIfUnique(_variables, EntityChildUniquenessKey::fromVar, variable);
   }
 
   public void addCategory(VariableDef category) {
diff --git a/src/main/java/org/veupathdb/service/eda/common/plugin/util/PluginUtil.java b/src/main/java/org/veupathdb/service/eda/common/plugin/util/PluginUtil.java
index 7e5b93ed..f58e91c5 100644
--- a/src/main/java/org/veupathdb/service/eda/common/plugin/util/PluginUtil.java
+++ b/src/main/java/org/veupathdb/service/eda/common/plugin/util/PluginUtil.java
@@ -63,7 +63,9 @@ private String getCollectionAttribute(Function<CollectionDef, ?> getter, Collect
   }
 
   private String getVariableAttribute(Function<VariableDef, ?> getter, VariableSpec var) {
-    return var == null ? "" : getter.apply(_metadata.getVariable(var).orElseThrow()).toString();
+    return var == null ? "" : getter.apply(_metadata.getVariable(var)
+        .orElseThrow(() -> new IllegalArgumentException(
+            String.format("Unable to find variable with spec %s, %s", var.getEntityId(), var.getVariableId())))).toString();
   }
 
   public String getCollectionType(CollectionSpec collection) {