diff --git a/snakebids/paths/_factory.py b/snakebids/paths/_factory.py
index 85648a04..a6bc3325 100644
--- a/snakebids/paths/_factory.py
+++ b/snakebids/paths/_factory.py
@@ -228,13 +228,21 @@ def bids(
 
         if datatype:
             path_parts.append(datatype)
+        tail = [suffix] if suffix is not None else []
         path_parts.append(
-            "_".join(it.chain(spec_parts[:split], custom_parts, spec_parts[split:]))
+            "_".join(
+                it.chain(
+                    spec_parts[:split],
+                    custom_parts,
+                    spec_parts[split:],
+                    tail,
+                )
+            )
         )
+        result = os.path.join(*path_parts)
+        if extension is not None:
+            result += extension
 
-        tail = f"_{suffix}{extension or ''}" if suffix else extension or ""
-
-        result = os.path.join(*path_parts) + tail
         if custom_parts and _implicit and not in_interactive_session():
             wrn_msg = (
                 f"Path generated with unrecognized entities, and a snakebids spec has "
diff --git a/snakebids/tests/test_paths/test_bids.py b/snakebids/tests/test_paths/test_bids.py
index ac905847..e6cc866a 100644
--- a/snakebids/tests/test_paths/test_bids.py
+++ b/snakebids/tests/test_paths/test_bids.py
@@ -144,6 +144,12 @@ def test_underscore_does_not_precede_extension(
         def test_no_underscore_at_end_if_no_suffix(self, entities: dict[str, str]):
             assert bids(**entities)[-1] != "_"
 
+        @given(entities=_bids_args(nonstandard=True, entities=None))
+        def test_no_underscore_at_beginning_if_only_suffix(
+            self, entities: dict[str, str]
+        ):
+            assert bids(**entities)[0] != "_"
+
         @given(entities=_bids_args(), root=_roots())
         def test_beginning_of_path_always_root(
             self, entities: dict[str, str], root: str
@@ -322,4 +328,6 @@ def test_benchmark_bids(benchmark: Benchmark):
         england="britain",
         space="cosmos",
         rome="fell",
+        suffix="suffix",
+        extension=".ext",
     )