diff --git a/csharp/ql/test/library-tests/dataflow/global/DataFlow.expected b/csharp/ql/test/library-tests/dataflow/global/DataFlow.expected
index 2e3cf9e831c41..3180b00f20597 100644
--- a/csharp/ql/test/library-tests/dataflow/global/DataFlow.expected
+++ b/csharp/ql/test/library-tests/dataflow/global/DataFlow.expected
@@ -82,6 +82,8 @@
 | GlobalDataFlow.cs:533:15:533:21 | access to field field |
 | GlobalDataFlow.cs:539:15:539:22 | access to field field |
 | GlobalDataFlow.cs:547:15:547:21 | access to field field |
+| MultiImplementationA.cs:7:39:7:39 | access to parameter x |
+| MultiImplementationB.cs:5:39:5:39 | access to parameter x |
 | Splitting.cs:9:15:9:15 | [b (line 3): false] access to local variable x |
 | Splitting.cs:9:15:9:15 | [b (line 3): true] access to local variable x |
 | Splitting.cs:11:19:11:19 | access to local variable x |
diff --git a/csharp/ql/test/library-tests/dataflow/global/DataFlowPath.expected b/csharp/ql/test/library-tests/dataflow/global/DataFlowPath.expected
index 46b01f0baeaaa..9b8f7aa390a82 100644
--- a/csharp/ql/test/library-tests/dataflow/global/DataFlowPath.expected
+++ b/csharp/ql/test/library-tests/dataflow/global/DataFlowPath.expected
@@ -451,6 +451,10 @@ edges
 | GlobalDataFlow.cs:556:27:556:27 | access to parameter e : null [element] : String | GlobalDataFlow.cs:558:46:558:46 | access to local variable x : String | provenance |  |
 | GlobalDataFlow.cs:558:46:558:46 | access to local variable x : String | GlobalDataFlow.cs:81:79:81:79 | x : String | provenance |  |
 | GlobalDataFlow.cs:558:46:558:46 | access to local variable x : String | GlobalDataFlow.cs:558:44:558:47 | delegate call : String | provenance |  |
+| MultiImplementationA.cs:5:28:5:41 | "taint source" : String | MultiImplementationA.cs:7:27:7:27 | x : String | provenance |  |
+| MultiImplementationA.cs:7:27:7:27 | x : String | MultiImplementationA.cs:7:39:7:39 | access to parameter x | provenance |  |
+| MultiImplementationA.cs:7:27:7:27 | x : String | MultiImplementationB.cs:5:39:5:39 | access to parameter x | provenance |  |
+| MultiImplementationB.cs:3:28:3:41 | "taint source" : String | MultiImplementationA.cs:7:27:7:27 | x : String | provenance |  |
 | Splitting.cs:3:28:3:34 | tainted : String | Splitting.cs:8:24:8:30 | [b (line 3): false] access to parameter tainted : String | provenance |  |
 | Splitting.cs:3:28:3:34 | tainted : String | Splitting.cs:8:24:8:30 | [b (line 3): true] access to parameter tainted : String | provenance |  |
 | Splitting.cs:8:13:8:13 | access to local variable x : String | Splitting.cs:9:15:9:15 | [b (line 3): false] access to local variable x | provenance |  |
@@ -904,6 +908,11 @@ nodes
 | GlobalDataFlow.cs:556:27:556:27 | access to parameter e : null [element] : String | semmle.label | access to parameter e : null [element] : String |
 | GlobalDataFlow.cs:558:44:558:47 | delegate call : String | semmle.label | delegate call : String |
 | GlobalDataFlow.cs:558:46:558:46 | access to local variable x : String | semmle.label | access to local variable x : String |
+| MultiImplementationA.cs:5:28:5:41 | "taint source" : String | semmle.label | "taint source" : String |
+| MultiImplementationA.cs:7:27:7:27 | x : String | semmle.label | x : String |
+| MultiImplementationA.cs:7:39:7:39 | access to parameter x | semmle.label | access to parameter x |
+| MultiImplementationB.cs:3:28:3:41 | "taint source" : String | semmle.label | "taint source" : String |
+| MultiImplementationB.cs:5:39:5:39 | access to parameter x | semmle.label | access to parameter x |
 | Splitting.cs:3:28:3:34 | tainted : String | semmle.label | tainted : String |
 | Splitting.cs:8:13:8:13 | access to local variable x : String | semmle.label | access to local variable x : String |
 | Splitting.cs:8:13:8:13 | access to local variable x : String | semmle.label | access to local variable x : String |
@@ -1075,5 +1084,9 @@ subpaths
 | GlobalDataFlow.cs:317:15:317:24 | access to parameter sinkParam8 | GlobalDataFlow.cs:18:27:18:40 | "taint source" : String | GlobalDataFlow.cs:317:15:317:24 | access to parameter sinkParam8 | access to parameter sinkParam8 |
 | GlobalDataFlow.cs:323:15:323:24 | access to parameter sinkParam9 | GlobalDataFlow.cs:211:46:211:59 | "taint source" : String | GlobalDataFlow.cs:323:15:323:24 | access to parameter sinkParam9 | access to parameter sinkParam9 |
 | Capture.cs:273:30:273:30 | access to parameter x | Capture.cs:273:34:273:47 | "taint source" : String | Capture.cs:273:30:273:30 | access to parameter x | access to parameter x |
+| MultiImplementationA.cs:7:39:7:39 | access to parameter x | MultiImplementationA.cs:5:28:5:41 | "taint source" : String | MultiImplementationA.cs:7:39:7:39 | access to parameter x | access to parameter x |
+| MultiImplementationA.cs:7:39:7:39 | access to parameter x | MultiImplementationB.cs:3:28:3:41 | "taint source" : String | MultiImplementationA.cs:7:39:7:39 | access to parameter x | access to parameter x |
+| MultiImplementationB.cs:5:39:5:39 | access to parameter x | MultiImplementationA.cs:5:28:5:41 | "taint source" : String | MultiImplementationB.cs:5:39:5:39 | access to parameter x | access to parameter x |
+| MultiImplementationB.cs:5:39:5:39 | access to parameter x | MultiImplementationB.cs:3:28:3:41 | "taint source" : String | MultiImplementationB.cs:5:39:5:39 | access to parameter x | access to parameter x |
 | GlobalDataFlow.cs:27:15:27:32 | access to property SinkProperty0 | GlobalDataFlow.cs:18:27:18:40 | "taint source" : String | GlobalDataFlow.cs:27:15:27:32 | access to property SinkProperty0 | access to property SinkProperty0 |
 | Splitting.cs:21:21:21:33 | call to method Return<String> | Splitting.cs:24:28:24:34 | tainted : String | Splitting.cs:21:21:21:33 | call to method Return<String> | call to method Return<String> |
diff --git a/csharp/ql/test/library-tests/dataflow/global/GetAnOutNode.expected b/csharp/ql/test/library-tests/dataflow/global/GetAnOutNode.expected
index ff1e94029b49b..ca13350d527b4 100644
--- a/csharp/ql/test/library-tests/dataflow/global/GetAnOutNode.expected
+++ b/csharp/ql/test/library-tests/dataflow/global/GetAnOutNode.expected
@@ -180,6 +180,8 @@
 | GlobalDataFlowStringBuilder.cs:44:9:44:18 | call to method Clear | normal | GlobalDataFlowStringBuilder.cs:44:9:44:18 | call to method Clear |
 | GlobalDataFlowStringBuilder.cs:45:23:45:35 | call to method ToString | normal | GlobalDataFlowStringBuilder.cs:45:23:45:35 | call to method ToString |
 | GlobalDataFlowStringBuilder.cs:49:21:49:33 | call to method ToString | normal | GlobalDataFlowStringBuilder.cs:49:21:49:33 | call to method ToString |
+| MultiImplementationA.cs:3:7:3:15 | call to constructor Object | normal | MultiImplementationA.cs:3:7:3:15 | call to constructor Object |
+| MultiImplementationB.cs:1:7:1:15 | call to constructor Object | normal | MultiImplementationB.cs:1:7:1:15 | call to constructor Object |
 | Splitting.cs:1:7:1:15 | call to constructor Object | normal | Splitting.cs:1:7:1:15 | call to constructor Object |
 | Splitting.cs:8:17:8:31 | [b (line 3): false] call to method Return<String> | normal | Splitting.cs:8:17:8:31 | [b (line 3): false] call to method Return<String> |
 | Splitting.cs:8:17:8:31 | [b (line 3): true] call to method Return<String> | normal | Splitting.cs:8:17:8:31 | [b (line 3): true] call to method Return<String> |
diff --git a/csharp/ql/test/library-tests/dataflow/global/MultiImplementationA.cs b/csharp/ql/test/library-tests/dataflow/global/MultiImplementationA.cs
new file mode 100644
index 0000000000000..624b1db7edc62
--- /dev/null
+++ b/csharp/ql/test/library-tests/dataflow/global/MultiImplementationA.cs
@@ -0,0 +1,10 @@
+// semmle-extractor-options: --separate-compilation
+
+class MultiImpl
+{
+    public void M1() => M2("taint source");
+
+    public void M2(string x) => Check(x);
+
+    static void Check<T>(T x) { }
+}
diff --git a/csharp/ql/test/library-tests/dataflow/global/MultiImplementationB.cs b/csharp/ql/test/library-tests/dataflow/global/MultiImplementationB.cs
new file mode 100644
index 0000000000000..f72888387618f
--- /dev/null
+++ b/csharp/ql/test/library-tests/dataflow/global/MultiImplementationB.cs
@@ -0,0 +1,8 @@
+class MultiImpl
+{
+    public void M1() => M2("taint source");
+
+    public void M2(string x) => Check(x);
+
+    static void Check<T>(T x) { }
+}
diff --git a/csharp/ql/test/library-tests/dataflow/global/TaintTracking.expected b/csharp/ql/test/library-tests/dataflow/global/TaintTracking.expected
index b83832f48a64d..8a68b204e0232 100644
--- a/csharp/ql/test/library-tests/dataflow/global/TaintTracking.expected
+++ b/csharp/ql/test/library-tests/dataflow/global/TaintTracking.expected
@@ -92,6 +92,8 @@
 | GlobalDataFlowStringBuilder.cs:37:15:37:19 | access to local variable sink1 |
 | GlobalDataFlowStringBuilder.cs:42:15:42:19 | access to local variable sink2 |
 | GlobalDataFlowStringBuilder.cs:50:15:50:19 | access to local variable sink3 |
+| MultiImplementationA.cs:7:39:7:39 | access to parameter x |
+| MultiImplementationB.cs:5:39:5:39 | access to parameter x |
 | Splitting.cs:9:15:9:15 | [b (line 3): false] access to local variable x |
 | Splitting.cs:9:15:9:15 | [b (line 3): true] access to local variable x |
 | Splitting.cs:11:19:11:19 | access to local variable x |
diff --git a/csharp/ql/test/library-tests/dataflow/global/TaintTrackingPath.expected b/csharp/ql/test/library-tests/dataflow/global/TaintTrackingPath.expected
index be1119200a271..6a317ec46cf90 100644
--- a/csharp/ql/test/library-tests/dataflow/global/TaintTrackingPath.expected
+++ b/csharp/ql/test/library-tests/dataflow/global/TaintTrackingPath.expected
@@ -503,6 +503,10 @@ edges
 | GlobalDataFlowStringBuilder.cs:49:13:49:17 | access to local variable sink3 : String | GlobalDataFlowStringBuilder.cs:50:15:50:19 | access to local variable sink3 | provenance |  |
 | GlobalDataFlowStringBuilder.cs:49:21:49:22 | access to local variable sb : StringBuilder | GlobalDataFlowStringBuilder.cs:49:21:49:33 | call to method ToString : String | provenance | MaD:1980 |
 | GlobalDataFlowStringBuilder.cs:49:21:49:33 | call to method ToString : String | GlobalDataFlowStringBuilder.cs:49:13:49:17 | access to local variable sink3 : String | provenance |  |
+| MultiImplementationA.cs:5:28:5:41 | "taint source" : String | MultiImplementationA.cs:7:27:7:27 | x : String | provenance |  |
+| MultiImplementationA.cs:7:27:7:27 | x : String | MultiImplementationA.cs:7:39:7:39 | access to parameter x | provenance |  |
+| MultiImplementationA.cs:7:27:7:27 | x : String | MultiImplementationB.cs:5:39:5:39 | access to parameter x | provenance |  |
+| MultiImplementationB.cs:3:28:3:41 | "taint source" : String | MultiImplementationA.cs:7:27:7:27 | x : String | provenance |  |
 | Splitting.cs:3:28:3:34 | tainted : String | Splitting.cs:8:24:8:30 | [b (line 3): false] access to parameter tainted : String | provenance |  |
 | Splitting.cs:3:28:3:34 | tainted : String | Splitting.cs:8:24:8:30 | [b (line 3): true] access to parameter tainted : String | provenance |  |
 | Splitting.cs:8:13:8:13 | access to local variable x : String | Splitting.cs:9:15:9:15 | [b (line 3): false] access to local variable x | provenance |  |
@@ -1011,6 +1015,11 @@ nodes
 | GlobalDataFlowStringBuilder.cs:49:21:49:22 | access to local variable sb : StringBuilder | semmle.label | access to local variable sb : StringBuilder |
 | GlobalDataFlowStringBuilder.cs:49:21:49:33 | call to method ToString : String | semmle.label | call to method ToString : String |
 | GlobalDataFlowStringBuilder.cs:50:15:50:19 | access to local variable sink3 | semmle.label | access to local variable sink3 |
+| MultiImplementationA.cs:5:28:5:41 | "taint source" : String | semmle.label | "taint source" : String |
+| MultiImplementationA.cs:7:27:7:27 | x : String | semmle.label | x : String |
+| MultiImplementationA.cs:7:39:7:39 | access to parameter x | semmle.label | access to parameter x |
+| MultiImplementationB.cs:3:28:3:41 | "taint source" : String | semmle.label | "taint source" : String |
+| MultiImplementationB.cs:5:39:5:39 | access to parameter x | semmle.label | access to parameter x |
 | Splitting.cs:3:28:3:34 | tainted : String | semmle.label | tainted : String |
 | Splitting.cs:8:13:8:13 | access to local variable x : String | semmle.label | access to local variable x : String |
 | Splitting.cs:8:13:8:13 | access to local variable x : String | semmle.label | access to local variable x : String |
@@ -1186,6 +1195,10 @@ subpaths
 | GlobalDataFlowStringBuilder.cs:37:15:37:19 | access to local variable sink1 | GlobalDataFlowStringBuilder.cs:30:35:30:48 | "taint source" : String | GlobalDataFlowStringBuilder.cs:37:15:37:19 | access to local variable sink1 | access to local variable sink1 |
 | GlobalDataFlowStringBuilder.cs:42:15:42:19 | access to local variable sink2 | GlobalDataFlowStringBuilder.cs:30:35:30:48 | "taint source" : String | GlobalDataFlowStringBuilder.cs:42:15:42:19 | access to local variable sink2 | access to local variable sink2 |
 | GlobalDataFlowStringBuilder.cs:50:15:50:19 | access to local variable sink3 | GlobalDataFlowStringBuilder.cs:48:47:48:60 | "taint source" : String | GlobalDataFlowStringBuilder.cs:50:15:50:19 | access to local variable sink3 | access to local variable sink3 |
+| MultiImplementationA.cs:7:39:7:39 | access to parameter x | MultiImplementationA.cs:5:28:5:41 | "taint source" : String | MultiImplementationA.cs:7:39:7:39 | access to parameter x | access to parameter x |
+| MultiImplementationA.cs:7:39:7:39 | access to parameter x | MultiImplementationB.cs:3:28:3:41 | "taint source" : String | MultiImplementationA.cs:7:39:7:39 | access to parameter x | access to parameter x |
+| MultiImplementationB.cs:5:39:5:39 | access to parameter x | MultiImplementationA.cs:5:28:5:41 | "taint source" : String | MultiImplementationB.cs:5:39:5:39 | access to parameter x | access to parameter x |
+| MultiImplementationB.cs:5:39:5:39 | access to parameter x | MultiImplementationB.cs:3:28:3:41 | "taint source" : String | MultiImplementationB.cs:5:39:5:39 | access to parameter x | access to parameter x |
 | Splitting.cs:9:15:9:15 | [b (line 3): false] access to local variable x | Splitting.cs:3:28:3:34 | tainted : String | Splitting.cs:9:15:9:15 | [b (line 3): false] access to local variable x | [b (line 3): false] access to local variable x |
 | Splitting.cs:9:15:9:15 | [b (line 3): true] access to local variable x | Splitting.cs:3:28:3:34 | tainted : String | Splitting.cs:9:15:9:15 | [b (line 3): true] access to local variable x | [b (line 3): true] access to local variable x |
 | Splitting.cs:11:19:11:19 | access to local variable x | Splitting.cs:3:28:3:34 | tainted : String | Splitting.cs:11:19:11:19 | access to local variable x | access to local variable x |