diff --git a/filters/kspread/qpro/libqpro/qpro/formula.h b/filters/kspread/qpro/libqpro/qpro/formula.h
index a0af2af68..c008aabca 100644
--- a/filters/kspread/qpro/libqpro/qpro/formula.h
+++ b/filters/kspread/qpro/libqpro/qpro/formula.h
@@ -35,7 +35,7 @@ protected:
 
 struct QpFormulaConv
 {
-   TQP_INT8       cOperand;
+   TQP_UINT8       cOperand;
    void        (*cFunc)(QpFormula& pThis, const char* pArg);
    const char*   cArg;
 };