diff --git a/becquerel/core/spectrum.py b/becquerel/core/spectrum.py
index 1e1181ff..8e088109 100644
--- a/becquerel/core/spectrum.py
+++ b/becquerel/core/spectrum.py
@@ -942,7 +942,7 @@ def __mul__(self, other):
     # This line adds the right multiplication
     __rmul__ = __mul__
 
-    def __div__(self, other):
+    def __truediv__(self, other):
         """Return a new Spectrum object with counts (or CPS) scaled down.
 
         Args:
@@ -958,9 +958,6 @@ def __div__(self, other):
 
         return self._mul_div(other, div=True)
 
-    # This line adds true division
-    __truediv__ = __div__
-
     def _mul_div(self, scaling_factor: float, div=False):
         """Multiply or divide a spectrum by a scalar. Handle errors.
 
diff --git a/becquerel/tools/isotope_qty.py b/becquerel/tools/isotope_qty.py
index 24be1575..fd9efa86 100644
--- a/becquerel/tools/isotope_qty.py
+++ b/becquerel/tools/isotope_qty.py
@@ -512,13 +512,8 @@ def __mul__(self, other):
 
         return self._mul_div(other, div=False)
 
-    def __div__(self, other):
-        """Divide the quantity"""
-
-        return self._mul_div(other, div=True)
-
     def __truediv__(self, other):
-        """Divide the quantity (python 3)"""
+        """Divide the quantity"""
 
         return self._mul_div(other, div=True)