diff --git a/src/check_builtin.cpp b/src/check_builtin.cpp
index 90048f004..e87c75e88 100644
--- a/src/check_builtin.cpp
+++ b/src/check_builtin.cpp
@@ -765,8 +765,10 @@ gb_internal bool check_builtin_c_procedure(CheckerContext *c, Operand *operand,
 			return false;
 		}
 
+		c->allow_c_vararg_param = true;
 		Operand args = {};
 		check_expr(c, &args, ce->args[1]);
+		c->allow_c_vararg_param = false;
 		if (list.mode == Addressing_Invalid) {
 			return false;
 		}
diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index 4709691c5..b71cec4d9 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -1968,6 +1968,14 @@ gb_internal Entity *check_ident(CheckerContext *c, Operand *o, Ast *n, Type *nam
 		break;
 
 	case Entity_Variable:
+		if ((e->flags & EntityFlag_CVarArg) && !c->allow_c_vararg_param) {
+			ERROR_BLOCK();
+			error(o->expr, "'#c_vararg' parameter '%.*s' cannot be used directly", LIT(name));
+			error_line("\tSuggestion: use c_va_start to convert C varargs to c_va_list\n");
+			o->mode = Addressing_Invalid;
+			o->type = t_invalid;
+			return e;
+		}
 		e->flags |= EntityFlag_Used;
 		if (type == t_invalid) {
 			o->type = t_invalid;
diff --git a/src/checker.hpp b/src/checker.hpp
index cd2e580d8..1a53018e3 100644
--- a/src/checker.hpp
+++ b/src/checker.hpp
@@ -834,6 +834,7 @@ struct CheckerContext {
 	bool       hide_polymorphic_errors;
 	bool       in_polymorphic_specialization;
 	bool       allow_arrow_right_selector_expr;
+	bool       allow_c_vararg_param;
 	u8         bit_field_bit_size;
 	Scope *    polymorphic_scope;