diff --git a/basic-geometry/matrix2x2.h b/basic-geometry/matrix2x2.h
index 6bf6541..613a322 100644
--- a/basic-geometry/matrix2x2.h
+++ b/basic-geometry/matrix2x2.h
@@ -113,6 +113,10 @@ inline int bgc_matrix2x2_is_singular_fp64(const BgcMatrix2x2FP64* matrix)
 
 inline int bgc_matrix2x2_is_rotation_fp32(const BgcMatrix2x2FP32* matrix)
 {
+    if (!bgc_is_unit_fp32(bgc_matrix2x2_get_determinant_fp32(matrix))) {
+        return 0;
+    }
+
     const float product_r1c1 = matrix->r1c1 * matrix->r1c1 + matrix->r1c2 * matrix->r2c1;
     const float product_r1c2 = matrix->r1c1 * matrix->r1c2 + matrix->r1c2 * matrix->r2c2;
 
@@ -125,6 +129,10 @@ inline int bgc_matrix2x2_is_rotation_fp32(const BgcMatrix2x2FP32* matrix)
 
 inline int bgc_matrix2x2_is_rotation_fp64(const BgcMatrix2x2FP64* matrix)
 {
+    if (!bgc_is_unit_fp64(bgc_matrix2x2_get_determinant_fp64(matrix))) {
+        return 0;
+    }
+
     const double product_r1c1 = matrix->r1c1 * matrix->r1c1 + matrix->r1c2 * matrix->r2c1;
     const double product_r1c2 = matrix->r1c1 * matrix->r1c2 + matrix->r1c2 * matrix->r2c2;
 
diff --git a/basic-geometry/matrix3x3.h b/basic-geometry/matrix3x3.h
index a716d67..b0bd7c6 100644
--- a/basic-geometry/matrix3x3.h
+++ b/basic-geometry/matrix3x3.h
@@ -276,6 +276,10 @@ inline int bgc_matrix3x3_is_singular_fp64(const BgcMatrix3x3FP64* matrix)
 
 inline int bgc_matrix3x3_is_rotation_fp32(const BgcMatrix3x3FP32* matrix)
 {
+    if (!bgc_is_unit_fp32(bgc_matrix3x3_get_determinant_fp32(matrix))) {
+        return 0;
+    }
+
     const float product_r1c1 = matrix->r1c1 * matrix->r1c1 + matrix->r1c2 * matrix->r2c1 + matrix->r1c3 * matrix->r3c1;
     const float product_r1c2 = matrix->r1c1 * matrix->r1c2 + matrix->r1c2 * matrix->r2c2 + matrix->r1c3 * matrix->r3c2;
     const float product_r1c3 = matrix->r1c1 * matrix->r1c3 + matrix->r1c2 * matrix->r2c3 + matrix->r1c3 * matrix->r3c3;
@@ -295,6 +299,10 @@ inline int bgc_matrix3x3_is_rotation_fp32(const BgcMatrix3x3FP32* matrix)
 
 inline int bgc_matrix3x3_is_rotation_fp64(const BgcMatrix3x3FP64* matrix)
 {
+    if (!bgc_is_unit_fp64(bgc_matrix3x3_get_determinant_fp64(matrix))) {
+        return 0;
+    }
+
     const double product_r1c1 = matrix->r1c1 * matrix->r1c1 + matrix->r1c2 * matrix->r2c1 + matrix->r1c3 * matrix->r3c1;
     const double product_r1c2 = matrix->r1c1 * matrix->r1c2 + matrix->r1c2 * matrix->r2c2 + matrix->r1c3 * matrix->r3c2;
     const double product_r1c3 = matrix->r1c1 * matrix->r1c3 + matrix->r1c2 * matrix->r2c3 + matrix->r1c3 * matrix->r3c3;