diff --git a/README.md b/README.md
index e60fb90..e56e520 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@ sta::math::matrix m_0 = sta::math::matrix::zeros(3,2);
 // Set specific entries in the matrix:
 m_0.set(0, 1, 4); // set the entry in the first column and second column to 0
 m_0.set(1, 0, 5);
-m_0.set(2, 2, 99);
+//m_0.set(2, 2, 99); -> Column index out of range
 
 // Display the matrix:
 m_0.show_serial();
diff --git a/src/linalg/matrix.cpp b/src/linalg/matrix.cpp
index ab3ae88..72b6e89 100644
--- a/src/linalg/matrix.cpp
+++ b/src/linalg/matrix.cpp
@@ -329,7 +329,8 @@ float matrix::operator[](uint16_t i) {
 }
 
 uint16_t matrix::get_idx(uint8_t r, uint8_t c) {
-	STA_ASSERT_MSG(r * c <= get_size(), "Index out of bounds get_idx");
+	STA_ASSERT_MSG(c < get_cols(), "Column index out of bounds get_idx");
+	STA_ASSERT_MSG(r < get_rows(), "Row index out of bounds get_idx");
 
     return (r * get_cols()) + c;