diff --git a/src/Expr.cc b/src/Expr.cc
index 7e07a94bd2..3bcf9d96a5 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -220,9 +220,9 @@ bool Expr::CanAdd() const { return false; }
 
 bool Expr::CanDel() const { return false; }
 
-TypePtr Expr::AddType() const { return nullptr; }
+TypePtr Expr::AddType() const { return base_type(TYPE_VOID); }
 
-TypePtr Expr::DelType() const { return nullptr; }
+TypePtr Expr::DelType() const { return base_type(TYPE_VOID); }
 
 ValPtr Expr::Add(Frame* /* f */) { Internal("Expr::Add called"); }
 
diff --git a/src/script_opt/Expr.cc b/src/script_opt/Expr.cc
index cb2927c6de..bc8fa55248 100644
--- a/src/script_opt/Expr.cc
+++ b/src/script_opt/Expr.cc
@@ -730,9 +730,10 @@ ExprPtr AddExpr::BuildSub(const ExprPtr& op1, const ExprPtr& op2) {
 }
 
 ExprPtr AggrAddDelExpr::Reduce(Reducer* c, StmtPtr& red_stmt) {
-    if ( type )
-        return UnaryExpr::Reduce(c, red_stmt);
-
+    // In the future, if we use add/delete for list operations or such,
+    // then the following becomes germane.
+    // if ( type )
+    //     return UnaryExpr::Reduce(c, red_stmt);
     if ( c->Optimizing() )
         op = c->UpdateExpr(op);
 
diff --git a/testing/btest/Baseline/language.add-del-expr-void/out b/testing/btest/Baseline/language.add-del-expr-void/out
new file mode 100644
index 0000000000..2da5539a69
--- /dev/null
+++ b/testing/btest/Baseline/language.add-del-expr-void/out
@@ -0,0 +1,3 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+error in <...>/add-del-expr-void.zeek, line 10: can't assign void value (my_any1 = add my_set[3])
+error in <...>/add-del-expr-void.zeek, line 11: can't assign void value (my_any2 = delete my_set[5])
diff --git a/testing/btest/language/add-del-expr-void.zeek b/testing/btest/language/add-del-expr-void.zeek
new file mode 100644
index 0000000000..972f3b8f6b
--- /dev/null
+++ b/testing/btest/language/add-del-expr-void.zeek
@@ -0,0 +1,13 @@
+# @TEST-DOC: checks for type-checking for add/delete expressions
+#
+# @TEST-EXEC-FAIL: zeek -b %INPUT >out 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
+
+global my_set: set[count];
+
+event zeek_init()
+	{
+	local my_any1: any = add my_set[3];
+	local my_any2: any = delete my_set[5];
+	print my_any1, my_any2;
+	}