diff --git a/spreg/ols.py b/spreg/ols.py
index f532039..a88a3ea 100644
--- a/spreg/ols.py
+++ b/spreg/ols.py
@@ -470,12 +470,15 @@ def __init__(
                     "White test not available when standard errors are estimated by HAC or White correction.",
                 )
                 white_test = False
-        USER.check_spat_diag(spat_diag, w)
+
         x_constant, name_x, warn = USER.check_constant(x, name_x)
         set_warn(self, warn)
         self.name_x = USER.set_name_x(name_x, x_constant)
         
-        w = USER.check_weights(w, y, slx_lags=slx_lags)
+        if spat_diag or moran:
+            w = USER.check_weights(w, y, slx_lags=slx_lags, w_required=True)
+        else:
+            w = USER.check_weights(w, y, slx_lags=slx_lags)
         if slx_lags >0:
 #            lag_x = get_lags(w, x_constant[:, 1:], slx_lags)
 #            x_constant = np.hstack((x_constant, lag_x))
diff --git a/spreg/ols_regimes.py b/spreg/ols_regimes.py
index cc9eac9..dd6df85 100755
--- a/spreg/ols_regimes.py
+++ b/spreg/ols_regimes.py
@@ -436,10 +436,13 @@ def __init__(
                 "White test not available when standard errors are estimated by HAC or White correction.",
             )
             white_test = False
-        USER.check_spat_diag(spat_diag, w)
+
         x_constant, name_x, warn = USER.check_constant(x, name_x, just_rem=True)
         name_x = USER.set_name_x(name_x, x_constant, constant=True)
-        w = USER.check_weights(w, y, slx_lags=slx_lags)
+        if spat_diag or moran:
+            w = USER.check_weights(w, y, slx_lags=slx_lags, w_required=True)
+        else:
+            w = USER.check_weights(w, y, slx_lags=slx_lags)
         if slx_lags > 0:
             lag_x = get_lags(w, x_constant, slx_lags)
             x_constant = np.hstack((x_constant, lag_x))
diff --git a/spreg/twosls.py b/spreg/twosls.py
index c44937a..5bae2e1 100644
--- a/spreg/twosls.py
+++ b/spreg/twosls.py
@@ -474,10 +474,10 @@ def __init__(
                     "Spatial diagnostics are not available for HAC estimation. The spatial diagnostics have been disabled for this model.",
                 )
                 spat_diag = False
-        USER.check_spat_diag(spat_diag, w)
+
         x_constant, name_x, warn = USER.check_constant(x, name_x)
         self.name_x = USER.set_name_x(name_x, x_constant)
-        w = USER.check_weights(w, y, slx_lags=slx_lags)        
+        w = USER.check_weights(w, y, slx_lags=slx_lags, w_required=spat_diag)        
         if slx_lags>0:
 #            lag_x = get_lags(w, x_constant[:, 1:], slx_lags)
 #            x_constant = np.hstack((x_constant, lag_x))
diff --git a/spreg/twosls_regimes.py b/spreg/twosls_regimes.py
index abf89f8..5163fbc 100644
--- a/spreg/twosls_regimes.py
+++ b/spreg/twosls_regimes.py
@@ -384,11 +384,10 @@ def __init__(
                     "Spatial diagnostics are not available for HAC estimation. The spatial diagnostics have been disabled for this model.",
                 )
                 spat_diag = False
-        USER.check_spat_diag(spat_diag, w)
         x_constant, name_x, warn = USER.check_constant(x, name_x, just_rem=True)
         set_warn(self, warn)
         name_x = USER.set_name_x(name_x, x_constant, constant=True)
-        w = USER.check_weights(w, y, slx_lags=slx_lags)
+        w = USER.check_weights(w, y, slx_lags=slx_lags, w_required=spat_diag)
         if slx_lags > 0:
             lag_x = get_lags(w, x_constant, slx_lags)
             x_constant = np.hstack((x_constant, lag_x))
diff --git a/spreg/twosls_sp_regimes.py b/spreg/twosls_sp_regimes.py
index 7749108..a427a70 100644
--- a/spreg/twosls_sp_regimes.py
+++ b/spreg/twosls_sp_regimes.py
@@ -503,7 +503,6 @@ def __init__(
                     "Spatial diagnostics are not available for HAC estimation. The spatial diagnostics have been disabled for this model.",
                 )
                 spat_diag = False
-        USER.check_spat_diag(spat_diag, w)
         x_constant, name_x, warn = USER.check_constant(x, name_x, just_rem=True)
         set_warn(self, warn)
         name_x = USER.set_name_x(name_x, x_constant, constant=True)
diff --git a/spreg/user_output.py b/spreg/user_output.py
index 34bd3e2..993058e 100755
--- a/spreg/user_output.py
+++ b/spreg/user_output.py
@@ -544,7 +544,7 @@ def check_weights(w, y, w_required=False, time=False, slx_lags=0):
     # should not raise an exception
 
     """
-    if w_required == True or w != None or slx_lags > 0:
+    if w_required == True or (w is not None) or slx_lags > 0:
         if isinstance(w, graph.Graph):
             w = w.to_W()
             
@@ -644,7 +644,7 @@ def check_robust(robust, wk):
                 "invalid value passed to robust, see docs for valid options"
             )
 
-
+''' Deprecated in 1.6.1
 def check_spat_diag(spat_diag, w):
     """Check if there is a w parameter passed by the user if the user also
     requests spatial diagnostics.
@@ -684,7 +684,7 @@ def check_spat_diag(spat_diag, w):
     if spat_diag:
         if not isinstance(w, weights.W):
             raise Exception("w must be a libpysal.W object to run spatial diagnostics")
-
+'''
 
 def check_reg_list(regimes, name_regimes, n):
     """Check if the regimes parameter passed by the user is a valid list of