Index: kcalc.cpp
===================================================================
--- kcalc.cpp
+++ kcalc.cpp
@@ -1553,6 +1553,7 @@
 
 			// internally, we deal with C locale style numbers, we need to convert
 			QString val = calc_display->text();
+			val.remove(KNumber::groupSeparator());
 			val.replace(KNumber::decimalSeparator(), QLatin1String("."));
 			KCalcSettings::setValueConstant(button, val);