diff --git a/filterpy/kalman/EKF.py b/filterpy/kalman/EKF.py
index 5e83aec..06e9c42 100644
--- a/filterpy/kalman/EKF.py
+++ b/filterpy/kalman/EKF.py
@@ -406,7 +406,8 @@ class ExtendedKalmanFilter(object):
         mahalanobis : float
         """
         if self._mahalanobis is None:
-            self._mahalanobis = sqrt(float(dot(dot(self.y.T, self.SI), self.y)))
+            d2 = self.y.T @ self.SI @ self.y
+            self._mahalanobis = sqrt(np.asarray(d2).item())
         return self._mahalanobis
 
     def __repr__(self):
diff --git a/filterpy/kalman/fading_memory.py b/filterpy/kalman/fading_memory.py
index 36c9dcc..2c4d582 100644
--- a/filterpy/kalman/fading_memory.py
+++ b/filterpy/kalman/fading_memory.py
@@ -438,7 +438,7 @@ class FadingKalmanFilter(object):
         mahalanobis : float
         """
         if self._mahalanobis is None:
-            self._mahalanobis = sqrt(float(dot(dot(self.y.T, self.SI), self.y)))
+            self._mahalanobis = sqrt((self.y.T @ self.SI @ self.y).item())
         return self._mahalanobis
 
     def __repr__(self):
diff --git a/filterpy/kalman/kalman_filter.py b/filterpy/kalman/kalman_filter.py
index 994b596..0f72d85 100644
--- a/filterpy/kalman/kalman_filter.py
+++ b/filterpy/kalman/kalman_filter.py
@@ -1235,7 +1235,8 @@ class KalmanFilter(object):
         mahalanobis : float
         """
         if self._mahalanobis is None:
-            self._mahalanobis = sqrt(float(dot(dot(self.y.T, self.SI), self.y)))
+            d2 = dot(dot(self.y.T, self.SI), self.y)
+            self._mahalanobis = sqrt(np.asarray(d2).item())
         return self._mahalanobis
 
     @property
diff --git a/filterpy/kalman/tests/test_imm.py b/filterpy/kalman/tests/test_imm.py
index aa71fc2..ec2fdc1 100644
--- a/filterpy/kalman/tests/test_imm.py
+++ b/filterpy/kalman/tests/test_imm.py
@@ -176,8 +176,8 @@ def test_imm():
 
     zs = np.zeros((N, 2))
     for i in range(len(zs)):
-        zs[i, 0] = simxs[i, 0] + randn()*r
-        zs[i, 1] = simxs[i, 2] + randn()*r
+        zs[i, 0] = simxs[i, 0, 0] + randn()*r
+        zs[i, 1] = simxs[i, 2, 0] + randn()*r
 
     '''
     try:
diff --git a/filterpy/leastsq/least_squares.py b/filterpy/leastsq/least_squares.py
index 2610b14..6c5eb8f 100644
--- a/filterpy/leastsq/least_squares.py
+++ b/filterpy/leastsq/least_squares.py
@@ -129,7 +129,7 @@ class LeastSquaresFilter(object):
 
         if self._order == 0:
             K[0] = 1. / n
-            y = z - x
+            y = z - x[0]
             x[0] += K[0] * y
 
         elif self._order == 1: