diff --git a/sumpy/assignment_collection.py b/sumpy/assignment_collection.py
index 8aa07d813066f6dc0382a57e34c42f14ae8bced7..a12a17fd84b7158628c120a4626464fd288940bb 100644
--- a/sumpy/assignment_collection.py
+++ b/sumpy/assignment_collection.py
@@ -48,7 +48,14 @@ class _SymbolGenerator(object):
         from collections import defaultdict
         self.base_to_count = defaultdict(lambda: 0)
 
+    def _normalize(self, base):
+        # Strip off any _N suffix, to avoid generating conflicting names.
+        import re
+        base = re.split("_\d+$", base)[0]
+        return base if base != "" else "expr"
+
     def __call__(self, base="expr"):
+        base = self._normalize(base)
         count = self.base_to_count[base]
 
         def make_id_str(base, count):
diff --git a/test/test_codegen.py b/test/test_codegen.py
index 376a8fcf8a142da5867875f9b3fcc15df805fe72..c7b5e0bc357ace12ecc59d11ead7ac9af7d19b1d 100644
--- a/test/test_codegen.py
+++ b/test/test_codegen.py
@@ -61,6 +61,23 @@ def test_kill_trivial_assignments():
         ('u2', _s(6*x, 1))]
 
 
+def test_symbolic_assignment_name_uniqueness():
+    # https://gitlab.tiker.net/inducer/sumpy/issues/13
+    from sumpy.assignment_collection import SymbolicAssignmentCollection
+
+    sac = SymbolicAssignmentCollection({"s_0": 1})
+    sac.assign_unique("s_", 1)
+    sac.assign_unique("s_", 1)
+    assert len(sac.assignments) == 3
+
+    sac = SymbolicAssignmentCollection()
+    sac.assign_unique("s_0", 1)
+    sac.assign_unique("s_", 1)
+    sac.assign_unique("s_", 1)
+
+    assert len(sac.assignments) == 3
+
+
 # You can test individual routines by typing
 # $ python test_fmm.py 'test_sumpy_fmm(cl.create_some_context)'