diff --git a/src/glsl/ast.h b/src/glsl/ast.h
index 9b119edbb2f..c0350e7358e 100644
--- a/src/glsl/ast.h
+++ b/src/glsl/ast.h
@@ -307,7 +307,8 @@ private:
 class ast_aggregate_initializer : public ast_expression {
 public:
    ast_aggregate_initializer()
-      : ast_expression(ast_aggregate, NULL, NULL, NULL)
+      : ast_expression(ast_aggregate, NULL, NULL, NULL),
+        constructor_type(NULL)
    {
       /* empty */
    }