diff --git a/src/cmd/go/internal/fmtcmd/fmt.go b/src/cmd/go/internal/fmtcmd/fmt.go
index 0e5509edfa..8e4ef37281 100644
--- a/src/cmd/go/internal/fmtcmd/fmt.go
+++ b/src/cmd/go/internal/fmtcmd/fmt.go
@@ -60,7 +60,7 @@ func runFmt(cmd *base.Command, args []string) {
 		}()
 	}
 	for _, pkg := range load.PackagesAndErrors(args) {
-		if modload.Enabled() && !pkg.Module.Main {
+		if modload.Enabled() && pkg.Module != nil && !pkg.Module.Main {
 			if !printed {
 				fmt.Fprintf(os.Stderr, "go: not formatting packages in dependency modules\n")
 				printed = true
diff --git a/src/cmd/go/testdata/script/mod_gofmt_invalid.txt b/src/cmd/go/testdata/script/mod_gofmt_invalid.txt
new file mode 100644
index 0000000000..21edc7dc2f
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_gofmt_invalid.txt
@@ -0,0 +1,13 @@
+# Test for a crash in go fmt on invalid input when using modules.
+# Issue 26792.
+
+env GO111MODULE=on
+! go fmt x.go
+! stderr panic
+
+-- go.mod --
+module x
+
+-- x.go --
+// Missing package declaration.
+var V int