diff --git a/src/gui/util/qvalidator.cpp b/src/gui/util/qvalidator.cpp
index 2a81006657a..8a92bef1b74 100644
--- a/src/gui/util/qvalidator.cpp
+++ b/src/gui/util/qvalidator.cpp
@@ -9,6 +9,7 @@
 #include "private/qobject_p.h"
 #include "private/qlocale_p.h"
 #include "private/qnumeric_p.h"
+#include "private/qstringiterator_p.h"
 
 #include <limits.h>
 #include <cmath>
@@ -757,8 +758,19 @@ void QDoubleValidatorPrivate::fixupWithLocale(QString &input, QLocaleData::Numbe
         if (numMode == QLocaleData::DoubleStandardMode) {
             mode = 'f';
         } else {
-            // scientific mode can be either 'e' or 'E'
-            mode = input.contains(QChar::fromLatin1('E')) ? 'E' : 'e';
+            // Scientific mode can be either 'e' or 'E'
+            const QString exp = locale.exponential();
+            bool preferUpper = false;
+            QStringIterator scan(exp);
+            while (!preferUpper && scan.hasNext()) {
+                const char32_t ch = scan.next();
+                if (QChar::isUpper(ch))
+                    preferUpper = true;
+            }
+            if (preferUpper)
+                mode = input.contains(exp.toLower()) ? 'e' : 'E';
+            else // If case-free, we don't care which we use; otherwise, prefer lower.
+                mode = input.contains(exp.toUpper()) ? 'E' : 'e';
         }
         int precision;
         if (q->dec < 0) {