diff --git a/openmc/region.py b/openmc/region.py
index e0c05d6741..51e1820fee 100644
--- a/openmc/region.py
+++ b/openmc/region.py
@@ -105,17 +105,17 @@ class Region(ABC):
                 # If special character appears immediately after a non-operator,
                 # create a token with the appropriate half-space
                 if i_start >= 0:
-                    # When an opening parenthesis appears after a non-operator,
-                    # there's an implicit intersection operator between them
-                    if expression[i] == '(':
-                        tokens.append(' ')
-
                     j = int(expression[i_start:i])
                     if j < 0:
                         tokens.append(-surfaces[abs(j)])
                     else:
                         tokens.append(+surfaces[abs(j)])
 
+                    # When an opening parenthesis appears after a non-operator,
+                    # there's an implicit intersection operator between them
+                    if expression[i] == '(':
+                        tokens.append(' ')
+
                 if expression[i] in '()|~':
                     # For everything other than intersection, add the operator
                     # to the list of tokens
diff --git a/tests/unit_tests/test_region.py b/tests/unit_tests/test_region.py
index 2e517c9652..3197a8d724 100644
--- a/tests/unit_tests/test_region.py
+++ b/tests/unit_tests/test_region.py
@@ -208,7 +208,8 @@ def test_from_expression(reset):
     # Opening parenthesis immediately after halfspace
     r = openmc.Region.from_expression('1(2|-3)', surfs)
     assert str(r) == '(1 (2 | -3))'
-
+    r = openmc.Region.from_expression('-1|(1 2(-3))', surfs)
+    assert str(r) == '(-1 | (1 2 -3))'
 
 def test_translate_inplace():
     sph = openmc.Sphere()