diff --git a/basecalc.cpp b/basecalc.cpp
index 9fe6768..fe8eb32 100644
--- a/basecalc.cpp
+++ b/basecalc.cpp
@@ -24,7 +24,7 @@ int BaseCalculator::calculate(const Operation& op)
         break;
 
         case OpType::Modulo:
-        result += op.a % op.b;
+        result = op.a % op.b;
         break;
 
         case OpType::Special: