Switch to json-c 0.15 to avoid json-c#766.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f9cbe6d..9362f8e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -20,7 +20,7 @@
 FetchContent_Declare(
   json-c
   GIT_REPOSITORY https://github.com/json-c/json-c.git
-  GIT_TAG        d28ac67dde77566f53a97f22b4ea7cb36afe6582 # 4/6/2022
+  GIT_TAG        9021cdcdd01fc9dbcbe1f06391848c2ac915212f # 0.15
 )
 
 # Fetch b64-c from git repository.