diff --git a/CHANGES.rst b/CHANGES.rst
index 53da0e9053..c6f6ccfc33 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -23,6 +23,7 @@ RELEASE_next_patch (Unreleased)
 * Fix ``find_peaks`` GUIs call with laplacian/difference of gaussian methods (`#2622 <https://github.com/hyperspy/hyperspy/issues/2622>`_ and `#2647 <https://github.com/hyperspy/hyperspy/pull/2647>`_)
 * Added lazy reading support for FFT and DPC datasets in FEI emd datasets (`#2651 <https://github.com/hyperspy/hyperspy/pull/2651>`_).
 * Fix various future and deprecation warnings from numpy and scikit-learn (`#2646 <https://github.com/hyperspy/hyperspy/pull/2646>`_)
+* Improve error message when initialising SpanROI with left >= right (`#2604 <https://github.com/hyperspy/hyperspy/pull/2604>`_)
 
 
 Changelog
diff --git a/hyperspy/misc/label_position.py b/hyperspy/misc/label_position.py
index 2aba307abf..ed5a260bdc 100644
--- a/hyperspy/misc/label_position.py
+++ b/hyperspy/misc/label_position.py
@@ -219,9 +219,8 @@ def _text_parser(self, text_edge):
         element, subshell = text_edge.split('_')
 
         if subshell[-1].isdigit():
-            formatted = element+' '+'$\mathregular{'+subshell[0]+'_'+\
-                subshell[-1]+'}$'
+            formatted = f"{element} {subshell[0]}$_{subshell[-1]}$"
         else:
-            formatted = element+' '+'$\mathregular{'+subshell[0]+'}$'
+            formatted = f"{element} {subshell[0]}"
 
         return formatted
diff --git a/hyperspy/roi.py b/hyperspy/roi.py
index 2b55ab5c9f..c7c150139c 100644
--- a/hyperspy/roi.py
+++ b/hyperspy/roi.py
@@ -702,16 +702,16 @@ class SpanROI(BaseInteractiveROI):
     _ndim = 1
 
     def __init__(self, left, right):
-        super(SpanROI, self).__init__()
-        self._bounds_check = True   # Use reponsibly!
+        super().__init__()
+        self._bounds_check = True   # Use responsibly!
+        if left >= right:
+            raise ValueError(f"`left` ({left}) must be smaller than `right` ({right}).")
         self.left, self.right = left, right
 
     def __getitem__(self, *args, **kwargs):
         _tuple = (self.left, self.right)
         return _tuple.__getitem__(*args, **kwargs)
 
-
-
     def is_valid(self):
         return (t.Undefined not in (self.left, self.right) and
                 self.right >= self.left)
diff --git a/hyperspy/tests/utils/test_roi.py b/hyperspy/tests/utils/test_roi.py
index daf1f03d18..9f5415de4c 100644
--- a/hyperspy/tests/utils/test_roi.py
+++ b/hyperspy/tests/utils/test_roi.py
@@ -104,6 +104,12 @@ def test_point2d_getitem(self):
         r = Point2DROI(1, 2)
         assert tuple(r) == (1, 2)
 
+    def test_span_roi_init(self):
+        with pytest.raises(ValueError):
+            SpanROI(30, 15)
+        with pytest.raises(ValueError):
+            SpanROI(15, 15)
+
     def test_span_spectrum_nav(self):
         s = self.s_s
         r = SpanROI(15, 30)
diff --git a/hyperspy/ui_registry.py b/hyperspy/ui_registry.py
index 86566818c0..72207be9db 100644
--- a/hyperspy/ui_registry.py
+++ b/hyperspy/ui_registry.py
@@ -18,7 +18,7 @@
 
 """Registry of user interface widgets.
 
-Format {"tool_key" : {"toolkit" : <function(obj, display, \*\*kwargs)>}}
+Format {"tool_key" : {"toolkit" : <function(obj, display, **kwargs)>}}
 
 The ``tool_key`` is defined by the "model function" to which the widget provides
 and user interface. That function gets the widget function from this registry
diff --git a/hyperspy/utils/__init__.py b/hyperspy/utils/__init__.py
index a7407de172..a713d1f444 100644
--- a/hyperspy/utils/__init__.py
+++ b/hyperspy/utils/__init__.py
@@ -48,7 +48,7 @@
 
 
 def print_known_signal_types():
-    """Print all known `signal_type`\s
+    r"""Print all known `signal_type`\s
 
     This includes `signal_type`\s from all installed packages that
     extend HyperSpy.