diff --git a/doubleml/tests/test_did_external_predictions.py b/doubleml/tests/test_did_external_predictions.py
index 59a1e6f1..43138cf8 100644
--- a/doubleml/tests/test_did_external_predictions.py
+++ b/doubleml/tests/test_did_external_predictions.py
@@ -49,7 +49,7 @@ def doubleml_did_fixture(did_score, dml_procedure, n_rep):
     np.random.seed(3141)
     dml_did_ext.fit(external_predictions=ext_predictions)
 
-    res_dict = {"coef_normal": dml_did.coef, "coef_ext": dml_did_ext.coef}
+    res_dict = {"coef_normal": dml_did.coef[0], "coef_ext": dml_did_ext.coef[0]}
 
     return res_dict
 
diff --git a/doubleml/tests/test_didcs_external_predictions.py b/doubleml/tests/test_didcs_external_predictions.py
index 90aafaef..a1ffda5e 100644
--- a/doubleml/tests/test_didcs_external_predictions.py
+++ b/doubleml/tests/test_didcs_external_predictions.py
@@ -52,7 +52,7 @@ def doubleml_didcs_fixture(did_score, dml_procedure, n_rep):
     np.random.seed(3141)
     dml_did_cs_ext.fit(external_predictions=ext_predictions)
 
-    res_dict = {"coef_normal": dml_did_cs.coef, "coef_ext": dml_did_cs_ext.coef}
+    res_dict = {"coef_normal": dml_did_cs.coef[0], "coef_ext": dml_did_cs_ext.coef[0]}
 
     return res_dict
 
diff --git a/doubleml/tests/test_iivm_external_predictions.py b/doubleml/tests/test_iivm_external_predictions.py
index fc9d3665..548f2297 100644
--- a/doubleml/tests/test_iivm_external_predictions.py
+++ b/doubleml/tests/test_iivm_external_predictions.py
@@ -59,7 +59,7 @@ def adapted_doubleml_fixture(dml_procedure, n_rep):
     np.random.seed(3141)
     dml_iivm_ext.fit(external_predictions=ext_predictions)
 
-    res_dict = {"coef_normal": dml_iivm.coef, "coef_ext": dml_iivm_ext.coef}
+    res_dict = {"coef_normal": dml_iivm.coef[0], "coef_ext": dml_iivm_ext.coef[0]}
 
     return res_dict
 
diff --git a/doubleml/tests/test_lpq_external_predictions.py b/doubleml/tests/test_lpq_external_predictions.py
index be4b9f73..af46191f 100644
--- a/doubleml/tests/test_lpq_external_predictions.py
+++ b/doubleml/tests/test_lpq_external_predictions.py
@@ -62,7 +62,7 @@ def doubleml_lpq_fixture(dml_procedure, n_rep, normalize_ipw):
     np.random.seed(3141)
     dml_lpq_ext.fit(external_predictions=ext_predictions)
 
-    res_dict = {"coef_normal": dml_lpq.coef, "coef_ext": dml_lpq_ext.coef}
+    res_dict = {"coef_normal": dml_lpq.coef[0], "coef_ext": dml_lpq_ext.coef[0]}
 
     return res_dict
 
diff --git a/doubleml/tests/test_pliv_external_predictions.py b/doubleml/tests/test_pliv_external_predictions.py
index 562ebe7d..5a5eb097 100644
--- a/doubleml/tests/test_pliv_external_predictions.py
+++ b/doubleml/tests/test_pliv_external_predictions.py
@@ -85,7 +85,7 @@ def adapted_doubleml_fixture(score, dml_procedure, n_rep, dim_z):
         np.random.seed(3141)
         dml_pliv_ext.fit(external_predictions=ext_predictions)
 
-        res_dict = {"coef_normal": dml_pliv.coef, "coef_ext": dml_pliv_ext.coef}
+        res_dict = {"coef_normal": dml_pliv.coef[0], "coef_ext": dml_pliv_ext.coef[0]}
 
     return res_dict
 
diff --git a/doubleml/tests/test_plr_external_predictions.py b/doubleml/tests/test_plr_external_predictions.py
index 3946ca05..9d776710 100644
--- a/doubleml/tests/test_plr_external_predictions.py
+++ b/doubleml/tests/test_plr_external_predictions.py
@@ -82,7 +82,7 @@ def doubleml_plr_fixture(plr_score, dml_procedure, n_rep, set_ml_m_ext, set_ml_l
     np.random.seed(3141)
     dml_plr_ext.fit(external_predictions=ext_predictions)
 
-    res_dict = {"coef_normal": dml_plr.coef, "coef_ext": dml_plr_ext.coef}
+    res_dict = {"coef_normal": dml_plr.coef[0], "coef_ext": dml_plr_ext.coef[0]}
 
     return res_dict
 
diff --git a/doubleml/tests/test_pq_external_predictions.py b/doubleml/tests/test_pq_external_predictions.py
index a2962ab0..4f23800f 100644
--- a/doubleml/tests/test_pq_external_predictions.py
+++ b/doubleml/tests/test_pq_external_predictions.py
@@ -86,7 +86,7 @@ def doubleml_pq_fixture(dml_procedure, n_rep, normalize_ipw, set_ml_m_ext, set_m
         tol_rel = 1e-9
         tol_abs = 1e-4
 
-    res_dict = {"coef_normal": dml_pq.coef, "coef_ext": dml_pq_ext.coef, "tol_rel": tol_rel, "tol_abs": tol_abs}
+    res_dict = {"coef_normal": dml_pq.coef[0], "coef_ext": dml_pq_ext.coef[0], "tol_rel": tol_rel, "tol_abs": tol_abs}
 
     return res_dict