diff --git a/mathparse/mathparse.py b/mathparse/mathparse.py
index 8aaab68..7b99b13 100644
--- a/mathparse/mathparse.py
+++ b/mathparse/mathparse.py
@@ -85,19 +85,23 @@ def to_number(val) -> Union[int, float, str, Decimal]:
     """
     Convert a string to an int or float if possible.
     """
-    # If already a number (int, float, Decimal), return as-is
-    if isinstance(val, (int, float, Decimal)):
-        return val
+    # If already a number (Decimal), return as-is
+    if isinstance(val, Decimal):
+        return Decimal(val)
+
+    # Convert other numbers to Decimal
+    if isinstance(val, (int, float)):
+        return Decimal(val)
 
     # Check if it's a constant and convert
     if is_constant(val):
-        return mathwords.CONSTANTS[val]
+        return Decimal(mathwords.CONSTANTS[val])
 
     # Otherwise, try to convert string to number
     if is_int(val):
-        return int(val)
+        return Decimal(int(val))
     elif is_float(val):
-        return float(val)
+        return Decimal(float(val))
 
     return val
 
diff --git a/tests/test_complex_statements.py b/tests/test_complex_statements.py
index d79b439..0cc2b3c 100644
--- a/tests/test_complex_statements.py
+++ b/tests/test_complex_statements.py
@@ -78,3 +78,10 @@ def test_unicode_pi_in_expression(self):
         """
         result = mathparse.parse('π + 1')
         self.assertAlmostEqual(result, 3.141593 + 1, places=5)
+
+    def test_with_operations_and_single_numbers(self):
+        """
+        Test using the unicode π symbol in a complex expression.
+        """
+        result = mathparse.parse("(1 + 3 + 2.0 + 6) * 1")
+        self.assertAlmostEqual(result, 0.00012, places=5)