diff --git a/src/m_json.c b/src/m_json.c
index e4a65e43..833c7956 100644
--- a/src/m_json.c
+++ b/src/m_json.c
@@ -13,11 +13,55 @@
 
 #include "m_json.h"
 
+#include <stdio.h>
+#include "i_printf.h"
+
 #include "cjson/cJSON.h"
 
-json_t *JS_Open(const char *data)
+json_t *JS_Open(const char *type, version_t version, const char *data)
 {
-    return cJSON_Parse(data);
+    const char *s;
+
+    json_t *json = cJSON_Parse(data);
+    if (json == NULL)
+    {
+        I_Printf(VB_ERROR, "%s: error before %s", type, cJSON_GetErrorPtr());
+        return NULL;
+    }
+
+    json_t *js_type = JS_GetObject(json, "type");
+    if (!JS_IsString(js_type))
+    {
+        I_Printf(VB_ERROR, "%s: no type string", type);
+        return NULL;
+    }
+
+    s = JS_GetString(js_type);
+    if (strcmp(s, type))
+    {
+        I_Printf(VB_ERROR, "%s: wrong type %s", type, s);
+        return NULL;
+    }
+
+    json_t *js_version = JS_GetObject(json, "version");
+    if (!JS_IsString(js_version))
+    {
+        I_Printf(VB_ERROR, "%s: no version string", type);
+        return NULL;
+    }
+
+    s = JS_GetString(js_version);
+    version_t v = {0};
+    sscanf(s, "%d.%d.%d", &v.major, &v.minor, &v.revision);
+    if (v.major != version.major || v.minor != version.minor
+        || v.revision != version.revision)
+    {
+        I_Printf(VB_ERROR, "%s: wrong version %d.%d.%d", type, v.major, v.minor,
+                 v.revision);
+        return NULL;
+    }
+
+    return json;
 }
 
 void JS_Close(json_t *json)
diff --git a/src/m_json.h b/src/m_json.h
index d7082bd2..e595f0c7 100644
--- a/src/m_json.h
+++ b/src/m_json.h
@@ -18,7 +18,14 @@
 
 typedef struct cJSON json_t;
 
-json_t *JS_Open(const char *data);
+typedef struct
+{
+    int major;
+    int minor;
+    int revision;
+} version_t;
+
+json_t *JS_Open(const char *type, version_t version, const char *data);
 void JS_Close(json_t *json);
 
 json_t *JS_GetObject(json_t *json, const char *string);
diff --git a/src/r_skydefs.c b/src/r_skydefs.c
index 8efaff50..f7e87c13 100644
--- a/src/r_skydefs.c
+++ b/src/r_skydefs.c
@@ -136,10 +136,10 @@ skydefs_t *R_ParseSkyDefs(void)
         return NULL;
     }
 
-    json_t *json = JS_Open(W_CacheLumpNum(lumpnum, PU_CACHE));
+    json_t *json = JS_Open("skydefs", (version_t){1, 0, 0},
+                           W_CacheLumpNum(lumpnum, PU_CACHE));
     if (json == NULL)
     {
-        I_Printf(VB_ERROR, "JSON: Error parsing SKYDEFS");
         JS_Close(json);
         return NULL;
     }
diff --git a/src/wi_interlvl.c b/src/wi_interlvl.c
index bff85690..59ad0a02 100644
--- a/src/wi_interlvl.c
+++ b/src/wi_interlvl.c
@@ -153,10 +153,10 @@ static void ParseLevelLayer(json_t *json, interlevellayer_t *out)
 
 interlevel_t *WI_ParseInterlevel(const char *lumpname)
 {
-    json_t *json = JS_Open(W_CacheLumpName(lumpname, PU_CACHE));
+    json_t *json = JS_Open("interlevel", (version_t){1, 0, 0},
+                           W_CacheLumpName(lumpname, PU_CACHE));
     if (json == NULL)
     {
-        I_Printf(VB_ERROR, "Error parsing %s", lumpname);
         JS_Close(json);
         return NULL;
     }