diff --git a/operator-sum.go b/operator-sum.go
index 1a4cc6d..31ccdbf 100644
--- a/operator-sum.go
+++ b/operator-sum.go
@@ -53,6 +53,8 @@ func sumValues(plusTerm *term, leftValue, rightValue any) (v any, err error) {
 		c := leftDict.clone()
 		c.merge(rightDict)
 		v = c
+	} else if isFraction(leftValue) && isFraction(rightValue) {
+		v, err = sumAnyFract(leftValue, rightValue)
 	} else {
 		err = plusTerm.errIncompatibleTypes(leftValue, rightValue)
 	}