1 files changed, 2 insertions, 1 deletions
diff --git a/generic/tclIO.c b/generic/tclIO.c
index 0f79f1e..b8a79c2 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -6111,8 +6111,9 @@ ReadChars(
     int factor = *factorPtr;
     int dstLimit = TCL_UTF_MAX - 1 + toRead * factor / UTF_EXPANSION_FACTOR;
 
+    if (dstLimit <= 0) dstLimit = INT_MAX; /* avoid overflow */
     (void) TclGetStringFromObj(objPtr, &numBytes);
-    Tcl_AppendToObj(objPtr, NULL, dstLimit);
+    TclAppendUtfToUtf(objPtr, NULL, dstLimit);
     if (toRead == srcLen) {
 	unsigned int size;