diff --git a/src/corelib/global/qtenvironmentvariables.cpp b/src/corelib/global/qtenvironmentvariables.cpp
index 58682a2406c..f564a523a57 100644
--- a/src/corelib/global/qtenvironmentvariables.cpp
+++ b/src/corelib/global/qtenvironmentvariables.cpp
@@ -195,13 +195,15 @@ int qEnvironmentVariableIntValue(const char *varName, bool *ok) noexcept
 {
     static const int NumBinaryDigitsPerOctalDigit = 3;
     static const int MaxDigitsForOctalInt =
-        (std::numeric_limits<uint>::digits + NumBinaryDigitsPerOctalDigit - 1) / NumBinaryDigitsPerOctalDigit;
+        (std::numeric_limits<uint>::digits + NumBinaryDigitsPerOctalDigit - 1) / NumBinaryDigitsPerOctalDigit
+            + 1     // sign
+            + 1;    // "0" base prefix
 
     const auto locker = qt_scoped_lock(environmentMutex);
     size_t size;
 #ifdef Q_CC_MSVC
     // we provide a buffer that can hold any int value:
-    char buffer[MaxDigitsForOctalInt + 2]; // +1 for NUL +1 for optional '-'
+    char buffer[MaxDigitsForOctalInt + 1]; // +1 for the terminating null
     size_t dummy;
     if (getenv_s(&dummy, buffer, sizeof buffer, varName) != 0) {
         if (ok)
@@ -211,7 +213,7 @@ int qEnvironmentVariableIntValue(const char *varName, bool *ok) noexcept
     size = strlen(buffer);
 #else
     const char * const buffer = ::getenv(varName);
-    if (!buffer || (size = strlen(buffer)) > MaxDigitsForOctalInt + 2) {
+    if (!buffer || (size = strlen(buffer)) > MaxDigitsForOctalInt) {
         if (ok)
             *ok = false;
         return 0;
diff --git a/tests/auto/corelib/global/qgetputenv/tst_qgetputenv.cpp b/tests/auto/corelib/global/qgetputenv/tst_qgetputenv.cpp
index 96f2ce853c5..9f9fc8f534e 100644
--- a/tests/auto/corelib/global/qgetputenv/tst_qgetputenv.cpp
+++ b/tests/auto/corelib/global/qgetputenv/tst_qgetputenv.cpp
@@ -163,19 +163,27 @@ void tst_QGetPutEnv::intValue_data()
     ROW(-1, -1, true);
     ROW(-010, -8, true);
     ROW(-000000000000000000000000000000000000000000000000001, 0, false);
-    ROW(2147483648, 0, false);
     // ROW(0xffffffff, -1, true); // could be expected, but not how QByteArray::toInt() works
     ROW(0xffffffff, 0, false);
-    const int bases[] = {10, 8, 16};
-    for (size_t i = 0; i < sizeof bases / sizeof *bases; ++i) {
-        QTest::addRow("INT_MAX, base %d", bases[i])
-                << QByteArray::number(INT_MAX) << INT_MAX << true;
-        QTest::addRow("INT_MAX+1, base %d", bases[i])
-                << QByteArray::number(qlonglong(INT_MAX) + 1) << 0 << false;
-        QTest::addRow("INT_MIN, base %d", bases[i])
-                << QByteArray::number(INT_MIN) << INT_MIN << true;
-        QTest::addRow("INT_MIN-1, base %d", bases[i])
-                << QByteArray::number(qlonglong(INT_MIN) - 1) << 0 << false;
+
+    auto addNumWithBase = [](qlonglong num, int base) {
+        QByteArray text;
+        {
+            QTextStream s(&text);
+            s.setIntegerBase(base);
+            s << Qt::showbase << num;
+        }
+        QTestData &row = QTest::addRow("%s", text.constData()) << text;
+        if (num == int(num))
+            row << int(num) << true;
+        else
+            row << 0 << false;
+    };
+    for (int base : {10, 8, 16}) {
+        addNumWithBase(INT_MAX, base);
+        addNumWithBase(qlonglong(INT_MAX) + 1, base);
+        addNumWithBase(INT_MIN, base);
+        addNumWithBase(qlonglong(INT_MIN) - 1 , base);
     };
 }