diff --git a/src/cmd/go/internal/modindex/read.go b/src/cmd/go/internal/modindex/read.go
index daa85762be0..6ec3a6b3af6 100644
--- a/src/cmd/go/internal/modindex/read.go
+++ b/src/cmd/go/internal/modindex/read.go
@@ -112,6 +112,7 @@ func Get(modroot string) (*ModuleIndex, error) {
 	if modroot == "" {
 		panic("modindex.Get called with empty modroot")
 	}
+	modroot = filepath.Clean(modroot)
 	isModCache := str.HasFilePathPrefix(modroot, cfg.GOMODCACHE)
 	return openIndex(modroot, isModCache)
 }
@@ -217,7 +218,7 @@ func (mi *ModuleIndex) Packages() []string {
 
 // RelPath returns the path relative to the module's root.
 func (mi *ModuleIndex) RelPath(path string) string {
-	return str.TrimFilePathPrefix(path, mi.modroot)
+	return str.TrimFilePathPrefix(filepath.Clean(path), mi.modroot) // mi.modroot is already clean
 }
 
 // ImportPackage is the equivalent of build.Import given the information in ModuleIndex.
diff --git a/src/cmd/go/testdata/script/list_replace_absolute_windows.txt b/src/cmd/go/testdata/script/list_replace_absolute_windows.txt
new file mode 100644
index 00000000000..6f5d737aded
--- /dev/null
+++ b/src/cmd/go/testdata/script/list_replace_absolute_windows.txt
@@ -0,0 +1,37 @@
+# Test a replacement with an absolute path (so the path isn't
+# cleaned by having filepath.Abs called on it). This checks
+# whether the modindex logic cleans the modroot path before using
+# it.
+
+[!windows] [short] skip
+
+go run print_go_mod.go # use this program to write a go.mod with an absolute path
+cp stdout go.mod
+
+go list -modfile=go.mod all
+-- print_go_mod.go --
+//go:build ignore
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+    work := os.Getenv("WORK")
+fmt.Printf(`module example.com/mod
+
+require b.com v0.0.0
+
+replace b.com => %s\gopath\src/modb
+`,  work)
+}
+-- a.go --
+package a
+
+import _ "b.com/b"
+-- modb/go.mod --
+module b.com
+-- modb/b/b.go --
+package b