diff --git a/win32/build/confutils.js b/win32/build/confutils.js
index d93cfe4a681..46c4090b4f6 100644
--- a/win32/build/confutils.js
+++ b/win32/build/confutils.js
@@ -2880,7 +2880,9 @@ function toolset_setup_project_tools()
 	}
 
 	/* TODO throw error, ignore for now for BC. */
-	PATH_PROG('sed');
+	if (!PATH_PROG('sed')) {
+		ERROR('sed is required')
+	}
 
 	RE2C = PATH_PROG('re2c');
 	if (RE2C) {