diff --git a/src/widgets/widgets/qwidgetlinecontrol_p.h b/src/widgets/widgets/qwidgetlinecontrol_p.h
index b730b415f0d..f4df95865d0 100644
--- a/src/widgets/widgets/qwidgetlinecontrol_p.h
+++ b/src/widgets/widgets/qwidgetlinecontrol_p.h
@@ -280,6 +280,13 @@ public:
         cancelPasswordEchoTimer();
         m_echoMode = mode;
         m_passwordEchoEditing = false;
+
+        // If this control is used for password input, we want to minimize
+        // the possibility of string reallocation not to leak (parts of)
+        // the password.
+        if (m_echoMode != QLineEdit::Normal)
+            m_text.reserve(30);
+
         updateDisplayText();
     }