diff --git a/CHANGES b/CHANGES
index d1200e5e3..66281cc6d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -18,7 +18,9 @@ Pint Changelog
   (PR #1816)
 - Fix converting to offset units of higher dimension e.g. gauge pressure
   (PR #1949)
-  
+- Fix unhandled TypeError when auto_reduce_dimensions=True and non_int_type=Decimal
+  (PR #1853)
+
 
 0.23 (2023-12-08)
 -----------------
diff --git a/pint/testsuite/test_issues.py b/pint/testsuite/test_issues.py
index 1e0497e4a..2a0b7edf6 100644
--- a/pint/testsuite/test_issues.py
+++ b/pint/testsuite/test_issues.py
@@ -1179,6 +1179,13 @@ def test_issue1505():
     )  # unexpected fail (magnitude should be a decimal)
 
 
+def test_issue_1845():
+    ur = UnitRegistry(auto_reduce_dimensions=True, non_int_type=decimal.Decimal)
+    # before issue 1845 these inputs would have resulted in a TypeError
+    assert ur("km / h * m").units == ur.Quantity("meter ** 2 / hour")
+    assert ur("kW / min * W").units == ur.Quantity("watts ** 2 / minute")
+
+
 @pytest.mark.parametrize(
     "units,spec,expected",
     [
diff --git a/pint/util.py b/pint/util.py
index 0c40c5187..c7a7ec10c 100644
--- a/pint/util.py
+++ b/pint/util.py
@@ -495,7 +495,7 @@ def add(self: Self, key: str, value: Number) -> Self:
         UnitsContainer
             A copy of this container.
         """
-        newval = self._d[key] + value
+        newval = self._d[key] + self._normalize_nonfloat_value(value)
         new = self.copy()
         if newval:
             new._d[key] = newval
@@ -656,7 +656,7 @@ def __truediv__(self, other: Any):
 
         new = self.copy()
         for key, value in other.items():
-            new._d[key] -= value
+            new._d[key] -= self._normalize_nonfloat_value(value)
             if new._d[key] == 0:
                 del new._d[key]
 
@@ -670,6 +670,11 @@ def __rtruediv__(self, other: Any):
 
         return self**-1
 
+    def _normalize_nonfloat_value(self, value: Scalar) -> Scalar:
+        if not isinstance(value, int) and not isinstance(value, self._non_int_type):
+            return self._non_int_type(value)  # type: ignore[no-any-return]
+        return value
+
 
 class ParserHelper(UnitsContainer):
     """The ParserHelper stores in place the product of variables and