diff --git a/src/plugins/debugger/watchhandler.cpp b/src/plugins/debugger/watchhandler.cpp
index 07824735ebfb28428785e749b9f371cf188c53d0..053fcadcd199ea8915dc09342b8b9d4462239ec7 100644
--- a/src/plugins/debugger/watchhandler.cpp
+++ b/src/plugins/debugger/watchhandler.cpp
@@ -118,7 +118,7 @@ static QByteArray quoteUnprintable(const QByteArray &ba)
     QByteArray res;
     char buf[10];
     for (int i = 0, n = ba.size(); i != n; ++i) {
-        char c = ba.at(i);
+        unsigned char c = ba.at(i);
         if (isprint(c)) {
             res += c;
         } else {