diff --git a/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/Flows.expected b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/Flows.expected
new file mode 100644
index 00000000000..81332464f79
--- /dev/null
+++ b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/Flows.expected
@@ -0,0 +1,2 @@
+failures
+invalidModelRow
diff --git a/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/Flows.ql b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/Flows.ql
new file mode 100644
index 00000000000..d7e78660a05
--- /dev/null
+++ b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/Flows.ql
@@ -0,0 +1,72 @@
+import go
+import semmle.go.dataflow.ExternalFlow
+import CsvValidation
+import TestUtilities.InlineExpectationsTest
+
+class SummaryModelTest extends SummaryModelCsv {
+  override predicate row(string row) {
+    row =
+      [
+        //`namespace; type; subtypes; name; signature; ext; input; output; kind`
+        "github.com/nonexistent/test;;false;FunctionWithParameter;;;Argument[0];ReturnValue;value",
+        "github.com/nonexistent/test;;false;FunctionWithSliceParameter;;;ArrayElement of Argument[0];ReturnValue;value",
+        "github.com/nonexistent/test;;false;FunctionWithVarArgsParameter;;;ArrayElement of Argument[0];ReturnValue;value",
+        "github.com/nonexistent/test;;false;FunctionWithSliceOfStructsParameter;;;Field[github.com/nonexistent/test.A.Field] of ArrayElement of Argument[0];ReturnValue;value",
+        "github.com/nonexistent/test;;false;FunctionWithVarArgsOfStructsParameter;;;Field[github.com/nonexistent/test.A.Field] of ArrayElement of Argument[0];ReturnValue;value",
+      ]
+  }
+}
+
+class DataConfiguration extends DataFlow::Configuration {
+  DataConfiguration() { this = "data-configuration" }
+
+  override predicate isSource(DataFlow::Node source) {
+    source = any(DataFlow::CallNode c | c.getCalleeName() = "source").getResult(0)
+  }
+
+  override predicate isSink(DataFlow::Node sink) {
+    sink = any(DataFlow::CallNode c | c.getCalleeName() = "sink").getArgument(0)
+  }
+}
+
+class DataFlowTest extends InlineExpectationsTest {
+  DataFlowTest() { this = "DataFlowTest" }
+
+  override string getARelevantTag() { result = "dataflow" }
+
+  override predicate hasActualResult(string file, int line, string element, string tag, string value) {
+    tag = "dataflow" and
+    exists(DataFlow::Node sink | any(DataConfiguration c).hasFlow(_, sink) |
+      element = sink.toString() and
+      value = "" and
+      sink.hasLocationInfo(file, line, _, _, _)
+    )
+  }
+}
+
+class TaintConfiguration extends TaintTracking::Configuration {
+  TaintConfiguration() { this = "taint-configuration" }
+
+  override predicate isSource(DataFlow::Node source) {
+    source = any(DataFlow::CallNode c | c.getCalleeName() = "source").getResult(0)
+  }
+
+  override predicate isSink(DataFlow::Node sink) {
+    sink = any(DataFlow::CallNode c | c.getCalleeName() = "sink").getArgument(0)
+  }
+}
+
+class TaintFlowTest extends InlineExpectationsTest {
+  TaintFlowTest() { this = "TaintFlowTest" }
+
+  override string getARelevantTag() { result = "taintflow" }
+
+  override predicate hasActualResult(string file, int line, string element, string tag, string value) {
+    tag = "taintflow" and
+    exists(DataFlow::Node sink | any(TaintConfiguration c).hasFlow(_, sink) |
+      element = sink.toString() and
+      value = "" and
+      sink.hasLocationInfo(file, line, _, _, _)
+    )
+  }
+}
diff --git a/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/go.mod b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/go.mod
new file mode 100644
index 00000000000..ed18764ed28
--- /dev/null
+++ b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/go.mod
@@ -0,0 +1,5 @@
+module semmle.go.Packages
+
+go 1.17
+
+require github.com/nonexistent/test v0.0.0-20200203000000-0000000000000
diff --git a/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/main.go b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/main.go
new file mode 100644
index 00000000000..40c2d31149b
--- /dev/null
+++ b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/main.go
@@ -0,0 +1,38 @@
+package main
+
+import (
+	"github.com/nonexistent/test"
+)
+
+func source() string {
+	return "untrusted data"
+}
+
+func sink(string) {
+}
+
+func main() {
+	s := source()
+	sink(test.FunctionWithParameter(s)) // $ taintflow dataflow
+
+	stringSlice := []string{source()}
+	sink(stringSlice[0]) // $ taintflow dataflow
+
+	s0 := ""
+	s1 := source()
+	sSlice := []string{s0, s1}
+	sink(test.FunctionWithParameter(sSlice[1]))        // $ taintflow dataflow
+	sink(test.FunctionWithSliceParameter(sSlice))      // $ taintflow dataflow
+	sink(test.FunctionWithVarArgsParameter(sSlice...)) // $ taintflow dataflow
+	sink(test.FunctionWithVarArgsParameter(s0, s1))    // $ MISSING: taintflow dataflow
+
+	sliceOfStructs := []test.A{{Field: source()}}
+	sink(sliceOfStructs[0].Field) // $ taintflow dataflow
+
+	a0 := test.A{Field: ""}
+	a1 := test.A{Field: source()}
+	aSlice := []test.A{a0, a1}
+	sink(test.FunctionWithSliceOfStructsParameter(aSlice))      // $ taintflow dataflow
+	sink(test.FunctionWithVarArgsOfStructsParameter(aSlice...)) // $ taintflow dataflow
+	sink(test.FunctionWithVarArgsOfStructsParameter(a0, a1))    // $ MISSING: taintflow dataflow
+}
diff --git a/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/semmle.go.Packages b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/semmle.go.Packages
new file mode 100755
index 00000000000..e3880ac8d5d
Binary files /dev/null and b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/semmle.go.Packages differ
diff --git a/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/vendor/github.com/nonexistent/test/stub.go b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/vendor/github.com/nonexistent/test/stub.go
new file mode 100644
index 00000000000..66f3da7d659
--- /dev/null
+++ b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/vendor/github.com/nonexistent/test/stub.go
@@ -0,0 +1,25 @@
+package test
+
+type A struct {
+	Field string
+}
+
+func FunctionWithParameter(s string) string {
+	return ""
+}
+
+func FunctionWithSliceParameter(s []string) string {
+	return ""
+}
+
+func FunctionWithVarArgsParameter(s ...string) string {
+	return ""
+}
+
+func FunctionWithSliceOfStructsParameter(s []A) string {
+	return ""
+}
+
+func FunctionWithVarArgsOfStructsParameter(s ...A) string {
+	return ""
+}
diff --git a/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/vendor/modules.txt b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/vendor/modules.txt
new file mode 100644
index 00000000000..b62dbf8819b
--- /dev/null
+++ b/ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/vendor/modules.txt
@@ -0,0 +1,3 @@
+# github.com/nonexistent/test v0.0.0-20200203000000-0000000000000
+## explicit
+github.com/nonexistent/test