diff --git a/lib/core/agent.py b/lib/core/agent.py
index c3e4b9a68..b7a79bc64 100644
--- a/lib/core/agent.py
+++ b/lib/core/agent.py
@@ -25,6 +25,7 @@ from lib.core.dicts import SQL_STATEMENTS
 from lib.core.enums import DBMS
 from lib.core.enums import PAYLOAD
 from lib.core.enums import PLACE
+from lib.core.enums import POST_HINT
 from lib.core.exception import sqlmapNoneDataException
 from lib.core.settings import CUSTOM_INJECTION_MARK_CHAR
 from lib.core.settings import GENERIC_SQL_COMMENT
@@ -111,7 +112,10 @@ class Agent:
         newValue = self.cleanupPayload(newValue, origValue)
 
         if place in (PLACE.URI, PLACE.CUSTOM_POST):
-            retVal = paramString.replace("%s%s" % (origValue, CUSTOM_INJECTION_MARK_CHAR), self.addPayloadDelimiters(newValue)).replace(CUSTOM_INJECTION_MARK_CHAR, "")
+            _ = "%s%s" % (origValue, CUSTOM_INJECTION_MARK_CHAR)
+            if kb.postHint == POST_HINT.JSON and not newValue.isdigit() and not '"%s"' % _ in paramString:
+                newValue = '"%s"' % newValue
+            retVal = paramString.replace(_, self.addPayloadDelimiters(newValue)).replace(CUSTOM_INJECTION_MARK_CHAR, "")
         elif place in (PLACE.USER_AGENT, PLACE.REFERER, PLACE.HOST):
             retVal = paramString.replace(origValue, self.addPayloadDelimiters(newValue))
         else:
diff --git a/lib/core/target.py b/lib/core/target.py
index 9468422f7..4aaba88da 100644
--- a/lib/core/target.py
+++ b/lib/core/target.py
@@ -93,8 +93,8 @@ def __setRequestParams():
             if test and test[0] in ("q", "Q"):
                 raise sqlmapUserQuitException
             elif test[0] not in ("n", "N"):
-                conf.data = re.sub(r'("[^"]+"\s*:\s*"[^"]+)"', r'\g<1>*"', conf.data)
-                conf.data = re.sub(r'("[^"]+"\s*:\s*)(-?[\d\.]+)', r'\g<1>"\g<2>*"', conf.data)
+                conf.data = re.sub(r'("[^"]+"\s*:\s*"[^"]+)"', r'\g<1>%s"' % CUSTOM_INJECTION_MARK_CHAR, conf.data)
+                conf.data = re.sub(r'("[^"]+"\s*:\s*)(-?[\d\.]+\b)', r'\g<0>%s' % CUSTOM_INJECTION_MARK_CHAR, conf.data)
                 kb.processUserMarks = True
                 kb.postHint = POST_HINT.JSON
 
diff --git a/lib/request/connect.py b/lib/request/connect.py
index 8d57d55af..e1832dc68 100644
--- a/lib/request/connect.py
+++ b/lib/request/connect.py
@@ -588,7 +588,10 @@ class Connect:
                     # with their HTML encoded counterparts
                     payload = payload.replace('>', "&gt;").replace('<', "&lt;")
                 elif kb.postHint == POST_HINT.JSON:
-                    payload = json.dumps(payload)[1:-1]
+                    if payload.startswith('"') and payload.endswith('"'):
+                        payload = json.dumps(payload[1:-1])
+                    else:
+                        payload = json.dumps(payload)[1:-1]
                 value = agent.replacePayload(value, payload)
 
             else: