src/cmd/go/internal/modload/import.go           | 10 ++++++----
 src/cmd/go/testdata/script/mod_install_hint.txt |  5 +++++

diff --git a/src/cmd/go/internal/modload/import.go b/src/cmd/go/internal/modload/import.go
index 995641c9f1f36d8a65192f6448e0c6f18c502fe4..eda0568f07d6456e6159816d48e571d7919c85bb 100644
--- a/src/cmd/go/internal/modload/import.go
+++ b/src/cmd/go/internal/modload/import.go
@@ -160,11 +160,13 @@ 	if e.importer == "" {
 		// Importing package is unknown, or the missing package was named on the
 		// command line. Recommend 'go mod download' for the modules that could
 		// provide the package, since that shouldn't change go.mod.
-		args := make([]string, len(e.mods))
-		for i, mod := range e.mods {
-			args[i] = mod.Path
+		if len(e.mods) > 0 {
+			args := make([]string, len(e.mods))
+			for i, mod := range e.mods {
+				args[i] = mod.Path
+			}
+			hint = fmt.Sprintf("; to add:\n\tgo mod download %s", strings.Join(args, " "))
 		}
-		hint = fmt.Sprintf("; to add:\n\tgo mod download %s", strings.Join(args, " "))
 	} else {
 		// Importing package is known (common case). Recommend 'go get' on the
 		// current version of the importing package.
diff --git a/src/cmd/go/testdata/script/mod_install_hint.txt b/src/cmd/go/testdata/script/mod_install_hint.txt
new file mode 100644
index 0000000000000000000000000000000000000000..ab02840eb8befb1f5579d7704e0fc8f5000f4232
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_install_hint.txt
@@ -0,0 +1,5 @@
+# Module is replaced but not required. No hint appears as no module is suggested.
+go mod init m
+go mod edit -replace=github.com/notrequired@v0.5.0=github.com/doesnotexist@v0.5.0
+! go install github.com/notrequired
+! stderr 'to add it:'
\ No newline at end of file