diff --git a/ssc/ast/nodes.functions.cs b/ssc/ast/nodes.functions.cs
index ad06105..be78dfb 100644
--- a/ssc/ast/nodes.functions.cs
+++ b/ssc/ast/nodes.functions.cs
@@ -16,6 +16,9 @@ namespace arookas {
 		public override void Compile(sunCompiler compiler) {
 			var symbol = compiler.Context.DeclareBuiltin(this);
 			symbol.Modifiers = Modifiers;
+			if ((symbol.Modifiers & sunSymbolModifiers.Local) != 0) {
+				throw new sunInvalidModifierException(this[0]); // local builtins are not supported
+			}
 		}
 	}
 
diff --git a/ssc/exceptions.cs b/ssc/exceptions.cs
index 3c76c69..26b004e 100644
--- a/ssc/exceptions.cs
+++ b/ssc/exceptions.cs
@@ -251,4 +251,12 @@ namespace arookas {
 		public sunContinueException(sunContinue node)
 			: base(node) { }
 	}
+	class sunInvalidModifierException : sunNodeException<sunNode> {
+		public override string Message {
+			get { return "Unsupported modifier in modifier list."; }
+		}
+
+		public sunInvalidModifierException(sunNode node)
+			: base(node) { }
+	}
 }