diff --git a/ql/src/semmle/go/frameworks/Stdlib.qll b/ql/src/semmle/go/frameworks/Stdlib.qll
index cee1e59676d..82210dce29b 100644
--- a/ql/src/semmle/go/frameworks/Stdlib.qll
+++ b/ql/src/semmle/go/frameworks/Stdlib.qll
@@ -146,35 +146,6 @@ module Fmt {
   }
 }
 
-/** Provides models of commonly used functions in the `io/ioutil` package. */
-module IoUtil {
-  private class IoUtilFileSystemAccess extends FileSystemAccess::Range, DataFlow::CallNode {
-    IoUtilFileSystemAccess() {
-      exists(string fn | getTarget().hasQualifiedName("io/ioutil", fn) |
-        fn = "ReadDir" or
-        fn = "ReadFile" or
-        fn = "TempDir" or
-        fn = "TempFile" or
-        fn = "WriteFile"
-      )
-    }
-
-    override DataFlow::Node getAPathArgument() { result = getAnArgument() }
-  }
-
-  /**
-   * A taint model of the `ioutil.ReadAll` function, recording that it propagates taint
-   * from its first argument to its first result.
-   */
-  private class ReadAll extends TaintTracking::FunctionModel {
-    ReadAll() { hasQualifiedName("io/ioutil", "ReadAll") }
-
-    override predicate hasTaintFlow(FunctionInput inp, FunctionOutput outp) {
-      inp.isParameter(0) and outp.isResult(0)
-    }
-  }
-}
-
 /** Provides models of commonly used functions in the `os` package. */
 module OS {
   /**
diff --git a/ql/src/semmle/go/frameworks/stdlib/IoIoutil.qll b/ql/src/semmle/go/frameworks/stdlib/IoIoutil.qll
new file mode 100644
index 00000000000..e59de928049
--- /dev/null
+++ b/ql/src/semmle/go/frameworks/stdlib/IoIoutil.qll
@@ -0,0 +1,56 @@
+/**
+ * Provides classes modeling security-relevant aspects of the `io/ioutil` package.
+ */
+
+import go
+
+/** Provides models of commonly used functions in the `io/ioutil` package. */
+module IoIoutil {
+  private class IoUtilFileSystemAccess extends FileSystemAccess::Range, DataFlow::CallNode {
+    IoUtilFileSystemAccess() {
+      exists(string fn | getTarget().hasQualifiedName("io/ioutil", fn) |
+        fn = "ReadDir" or
+        fn = "ReadFile" or
+        fn = "TempDir" or
+        fn = "TempFile" or
+        fn = "WriteFile"
+      )
+    }
+
+    override DataFlow::Node getAPathArgument() { result = getAnArgument() }
+  }
+
+  private class FunctionModels extends TaintTracking::FunctionModel {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    FunctionModels() {
+      // signature: func NopCloser(r io.Reader) io.ReadCloser
+      hasQualifiedName("io/ioutil", "NopCloser") and
+      (inp.isParameter(0) and outp.isResult())
+      or
+      // signature: func ReadAll(r io.Reader) ([]byte, error)
+      hasQualifiedName("io/ioutil", "ReadAll") and
+      (inp.isParameter(0) and outp.isResult(0))
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+
+  private class MethodModels extends TaintTracking::FunctionModel, Method {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    MethodModels() {
+      // signature: func (Writer).Write(p []byte) (n int, err error)
+      this.implements("io", "Writer", "Write") and
+      (inp.isParameter(0) and outp.isReceiver())
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+}
diff --git a/ql/test/library-tests/semmle/go/frameworks/StdlibTaintFlow/IoIoutil.go b/ql/test/library-tests/semmle/go/frameworks/StdlibTaintFlow/IoIoutil.go
new file mode 100644
index 00000000000..6e7b87090ed
--- /dev/null
+++ b/ql/test/library-tests/semmle/go/frameworks/StdlibTaintFlow/IoIoutil.go
@@ -0,0 +1,45 @@
+// Code generated by https://github.com/gagliardetto/codebox. DO NOT EDIT.
+
+package main
+
+import (
+	"io"
+	"io/ioutil"
+)
+
+func TaintStepTest_IoIoutilNopCloser_B0I0O0(sourceCQL interface{}) interface{} {
+	fromReader656 := sourceCQL.(io.Reader)
+	intoReadCloser414 := ioutil.NopCloser(fromReader656)
+	return intoReadCloser414
+}
+
+func TaintStepTest_IoIoutilReadAll_B0I0O0(sourceCQL interface{}) interface{} {
+	fromReader518 := sourceCQL.(io.Reader)
+	intoByte650, _ := ioutil.ReadAll(fromReader518)
+	return intoByte650
+}
+
+func TaintStepTest_IoWriterWrite_B0I0O0(sourceCQL interface{}) interface{} {
+	fromByte784 := sourceCQL.([]byte)
+	var intoWriter957 io.Writer
+	intoWriter957.Write(fromByte784)
+	return intoWriter957
+}
+
+func RunAllTaints_IoIoutil() {
+	{
+		source := newSource(0)
+		out := TaintStepTest_IoIoutilNopCloser_B0I0O0(source)
+		sink(0, out)
+	}
+	{
+		source := newSource(1)
+		out := TaintStepTest_IoIoutilReadAll_B0I0O0(source)
+		sink(1, out)
+	}
+	{
+		source := newSource(2)
+		out := TaintStepTest_IoWriterWrite_B0I0O0(source)
+		sink(2, out)
+	}
+}