Taken from upstream: https://github.com/open-source-parsers/jsoncpp/issues/1235.

From ac2870298ed5b5a96a688d9df07461b31f83e906 Mon Sep 17 00:00:00 2001
From: Derick Vigne <derickvigne@me.com>
Date: Tue, 26 Jan 2021 14:59:12 -0500
Subject: [PATCH] Fixed pkg-config Version

---
 pkg-config/jsoncpp.pc.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg-config/jsoncpp.pc.in b/pkg-config/jsoncpp.pc.in
index 632a377f5..2a2221069 100644
--- a/pkg-config/jsoncpp.pc.in
+++ b/pkg-config/jsoncpp.pc.in
@@ -5,7 +5,7 @@ includedir=@includedir_for_pc_file@
 
 Name: jsoncpp
 Description: A C++ library for interacting with JSON
-Version: @JSONCPP_VERSION@
+Version: @PROJECT_VERSION@
 URL: https://github.com/open-source-parsers/jsoncpp
 Libs: -L${libdir} -ljsoncpp
 Cflags: -I${includedir}