diff --git a/qpms/cyquaternions.pyx b/qpms/cyquaternions.pyx
index 823b82c..0797146 100644
--- a/qpms/cyquaternions.pyx
+++ b/qpms/cyquaternions.pyx
@@ -2,6 +2,7 @@ from .cybspec cimport BaseSpec
 from .qpms_cdefs cimport *
 import cmath
 import math
+import numpy as np
 
 
 def complex_crep(complex c, parentheses = False, shortI = True, has_Imaginary = False):
@@ -148,9 +149,22 @@ cdef class CQuat:
     
     @staticmethod
     def from_rotvector(vec):
+        '''
+        Constructs a quaternion representing rotation around a given rotation vector.
+
+        Parameters
+        ----------
+        vec: array_like of shape (3,)
+            Cartesian components of the rotation vector.
+
+        Returns
+        -------
+        CQuat
+        '''
+        vec = np.array(vec, copy=False)
         if vec.shape != (3,):
             raise ValueError("Single 3d vector expected")
-        res = CQuat()
+        res = CQuat(0,0,0,0)
         cdef cart3_t v
         v.x = vec[0]
         v.y = vec[1]