diff --git a/prospr/_version.py b/prospr/_version.py
index fc0b1c7..70f1ec7 100644
--- a/prospr/_version.py
+++ b/prospr/_version.py
@@ -1 +1 @@
-__version__ = "1.2.17"
+__version__ = "1.2.18"
diff --git a/prospr/visualize.py b/prospr/visualize.py
index 3655ec5..29f2911 100644
--- a/prospr/visualize.py
+++ b/prospr/visualize.py
@@ -493,6 +493,9 @@ def plot_protein(
                 protein, df, ax, linewidth, markersize, annotate_first
             )
 
+    # Transform axis limits to make protein segments squared.
+    ax.axis("equal")
+
     # If adding legend, remove title from legend and add item for bonds.
     if legend:
         handles, labels = ax.get_legend_handles_labels()
@@ -520,7 +523,8 @@ def plot_protein(
                 linestyle="None",
                 markerfacecolor="white",
                 markeredgecolor=COLOR_ANNOTATE,
-                markeredgewidth=2,
+                markeredgewidth=1.75,
+                markersize=10,
                 label="Head",
             )
             handles.append(annotate_patch)
diff --git a/tests/visualize/test_visualization.py b/tests/visualize/test_visualization.py
index fcffbcc..1de42c5 100644
--- a/tests/visualize/test_visualization.py
+++ b/tests/visualize/test_visualization.py
@@ -66,6 +66,16 @@ def test_2d_visualization(self, show=False):
             show=False,
         )
 
+        p = Protein("HPPHPPPHPPPPPHH", dim=2, model="HP")
+        p.set_hash([-1, -2, 1, -2, 1, 2, 2, 1, 2, 2, -1, -1, -2, 1])
+        plot_protein(
+            p,
+            style="paper",
+            legend_style="outer",
+            annotate_first=True,
+            show=False,
+        )
+
         p = Protein("HHPHPHPPPHPHHHPPPPPPHPPPH", dim=2, model="HP")
         p.set_hash(
             [