diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -2163,12 +2163,12 @@ def _convert_dx(dx, x0, xconv, convert):
             # removes the units from unit packages like `pint` that
             # wrap numpy arrays.
             try:
-                x0 = x0[0]
+                x0 = cbook.safe_first_element(x0)
             except (TypeError, IndexError, KeyError):
                 x0 = x0
 
             try:
-                x = xconv[0]
+                x = cbook.safe_first_element(xconv)
             except (TypeError, IndexError, KeyError):
                 x = xconv
 

diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -1592,6 +1592,14 @@ def test_bar_pandas(pd):
     ax.plot(dates, baseline, color='orange', lw=4)
 
 
+def test_bar_pandas_indexed(pd):
+    # Smoke test for indexed pandas
+    df = pd.DataFrame({"x": [1., 2., 3.], "width": [.2, .4, .6]},
+                       index=[1, 2, 3])
+    fig, ax = plt.subplots()
+    ax.bar(df.x, 1., width=df.width)
+
+
 @image_comparison(baseline_images=['hist_log'],
                   remove_text=True)
 def test_hist_log():