diff --git a/matrix.ts b/matrix.ts
index 4c2df49..0f6bcb5 100644
--- a/matrix.ts
+++ b/matrix.ts
@@ -29,7 +29,7 @@ export class Matrix {
 	}
 
 	add(other_matrix: Matrix) {
-		if(!(other_matrix.cols == this.cols && other_matrix.rows == this.cols)) throw Error("Other matrix has more or few rows or columns");
+		if(!(other_matrix.cols == this.cols && other_matrix.rows == this.rows)) throw Error("Other matrix has more or few rows or columns");
 		for(let i=0; i<this.matrix.length; i++) {
 			for(let j=0; j<this.matrix[i].length; j++) {
 				this.matrix[i][j] += other_matrix.matrix[i][j];