diff --git a/frontends/ilang/ilang_parser.y b/frontends/ilang/ilang_parser.y
index 0df792997..44c99906a 100644
--- a/frontends/ilang/ilang_parser.y
+++ b/frontends/ilang/ilang_parser.y
@@ -47,6 +47,15 @@ USING_YOSYS_NAMESPACE
 
 %define api.prefix {rtlil_frontend_ilang_yy}
 
+/* The union is defined in the header, so we need to provide all the
+ * includes it requires
+ */
+%code requires {
+#include <string>
+#include <vector>
+#include "frontends/ilang/ilang_frontend.h"
+}
+
 %union {
 	char *string;
 	int integer;
@@ -451,4 +460,3 @@ conn_stmt:
 		delete $2;
 		delete $3;
 	};
-
diff --git a/frontends/verilog/verilog_parser.y b/frontends/verilog/verilog_parser.y
index d23009e60..e82c2781c 100644
--- a/frontends/verilog/verilog_parser.y
+++ b/frontends/verilog/verilog_parser.y
@@ -112,6 +112,15 @@ struct specify_rise_fall {
 
 %define api.prefix {frontend_verilog_yy}
 
+/* The union is defined in the header, so we need to provide all the
+ * includes it requires
+ */
+%code requires {
+#include <map>
+#include <string>
+#include "frontends/verilog/verilog_frontend.h"
+}
+
 %union {
 	std::string *string;
 	struct YOSYS_NAMESPACE_PREFIX AST::AstNode *ast;
@@ -2418,4 +2427,3 @@ concat_list:
 		$$ = $3;
 		$$->children.push_back($1);
 	};
-