1 files changed, 8 insertions, 7 deletions
diff --git a/ext/misc/json1.c b/ext/misc/json1.c
index 77641064d..5863cffbc 100644
--- a/ext/misc/json1.c
+++ b/ext/misc/json1.c
@@ -1959,11 +1959,7 @@ static void jsonGroupInverse(
   if( NEVER(!pStr) ) return;
 #endif
   z = pStr->zBuf;
-  for(i=1; (c = z[i])!=',' || inStr || nNest; i++){
-    if( i>=pStr->nUsed ){
-      pStr->nUsed = 1;
-      return;
-    }
+  for(i=1; i<pStr->nUsed && ((c = z[i])!=',' || inStr || nNest); i++){
     if( c=='"' ){
       inStr = !inStr;
     }else if( c=='\\' ){
@@ -1973,8 +1969,13 @@ static void jsonGroupInverse(
       if( c=='}' || c==']' ) nNest--;
     }
   }
-  pStr->nUsed -= i;      
-  memmove(&z[1], &z[i+1], (size_t)pStr->nUsed-1);
+  if( i<pStr->nUsed ){
+    pStr->nUsed -= i;
+    memmove(&z[1], &z[i+1], (size_t)pStr->nUsed-1);
+    z[pStr->nUsed] = 0;
+  }else{
+    pStr->nUsed = 1;
+  }
 }
 #else
 # define jsonGroupInverse 0