diff --git a/src/testlib/qtestcase.cpp b/src/testlib/qtestcase.cpp
index 62649441db..eae490e278 100644
--- a/src/testlib/qtestcase.cpp
+++ b/src/testlib/qtestcase.cpp
@@ -2514,7 +2514,7 @@ static bool debuggerPresent()
     if (fd == -1)
         return false;
     char buffer[2048];
-    ssize_t size = read(fd, buffer, sizeof(buffer));
+    ssize_t size = read(fd, buffer, sizeof(buffer) - 1);
     if (size == -1) {
         close(fd);
         return false;