diff --git a/econml/_shap.py b/econml/_shap.py
index 986ec152..cc417d71 100644
--- a/econml/_shap.py
+++ b/econml/_shap.py
@@ -82,7 +82,8 @@ def _shap_explain_cme(cme_model, X, d_t, d_y,
                                             data=shap_out.data, main_effects=shap_out.main_effects,
                                             feature_names=shap_out.feature_names)
             shap_outs[output_names[i]][treatment_names[0]] = shap_out_new
-    return shap_outs
+    # return plain dictionary so that erroneous accesses don't half work (see #708)
+    return dict(shap_outs)
 
 
 def _shap_explain_model_cate(cme_model, models, X, d_t, d_y, featurizer=None, feature_names=None,
@@ -176,7 +177,8 @@ def _shap_explain_model_cate(cme_model, models, X, d_t, d_y, featurizer=None, fe
         else:
             shap_outs[output_names[0]][treatment_names[i]] = shap_out
 
-    return shap_outs
+    # return plain dictionary so that erroneous accesses don't half work (see #708)
+    return dict(shap_outs)
 
 
 def _shap_explain_joint_linear_model_cate(model_final, X, d_t, d_y, fit_cate_intercept,
@@ -258,7 +260,8 @@ def _shap_explain_joint_linear_model_cate(model_final, X, d_t, d_y, fit_cate_int
                                             feature_names=shap_out.feature_names)
             shap_outs[output_names[0]][treatment_names[i]] = shap_out_new
 
-    return shap_outs
+    # return plain dictionary so that erroneous accesses don't half work (see #708)
+    return dict(shap_outs)
 
 
 def _shap_explain_multitask_model_cate(cme_model, multitask_model_cate, X, d_t, d_y, featurizer=None,
@@ -352,7 +355,8 @@ def _shap_explain_multitask_model_cate(cme_model, multitask_model_cate, X, d_t,
                 shap_outs[output_names[j]][treatment_names[i]] = shap_out_new
         else:
             shap_outs[output_names[j]][treatment_names[0]] = shap_out
-    return shap_outs
+    # return plain dictionary so that erroneous accesses don't half work (see #708)
+    return dict(shap_outs)
 
 
 def _define_names(d_t, d_y, treatment_names, output_names, feature_names, input_names, featurizer):
diff --git a/econml/utilities.py b/econml/utilities.py
index b31843f8..a7becc0a 100644
--- a/econml/utilities.py
+++ b/econml/utilities.py
@@ -1360,7 +1360,9 @@ def transpose_dictionary(d):
     for key1, value in d.items():
         for key2, val in value.items():
             output[key2][key1] = val
-    return output
+
+    # return plain dictionary so that erroneous accesses don't half work (see e.g. #708)
+    return dict(output)
 
 
 def reshape_arrays_2dim(length, *args):