diff --git a/imports/fix_test.go b/imports/fix_test.go
index 2197bafd..d39f28ff 100644
--- a/imports/fix_test.go
+++ b/imports/fix_test.go
@@ -5,6 +5,7 @@
 package imports
 
 import (
+	"bufio"
 	"bytes"
 	"flag"
 	"go/build"
@@ -1957,3 +1958,95 @@ var _ = &bytes.Buffer{}
 		}
 	})
 }
+
+// A happy path test for Process
+func TestProcess(t *testing.T) {
+	in := `package testimports
+
+	var s = fmt.Sprintf("%s", "value")
+`
+	out, err := Process("foo", []byte(in), nil)
+
+	if err != nil {
+		t.Errorf("Process returned error.\n got:\n%v\nwant:\nnil", err)
+	}
+
+	want := `package testimports
+
+import "fmt"
+
+var s = fmt.Sprintf("%s", "value")
+`
+	if got := string(out); got != want {
+		t.Errorf("Process returned unexpected result.\ngot:\n%v\nwant:\n%v", got, want)
+	}
+}
+
+// Ensures a token as large as 500000 bytes can be handled
+// https://golang.org/issues/18201
+func TestProcessLargeToken(t *testing.T) {
+	largeString := strings.Repeat("x", 500000)
+
+	in := `package testimports
+
+import (
+	"fmt"
+	"mydomain.mystuff/mypkg"
+)
+
+const s = fmt.Sprintf("%s", "` + largeString + `")
+const x = mypkg.Sprintf("%s", "my package")
+
+// end
+`
+
+	out, err := Process("foo", []byte(in), nil)
+
+	if err != nil {
+		t.Errorf("Process returned error.\n got:\n%v\nwant:\nnil", err)
+	}
+
+	want := `package testimports
+
+import (
+	"fmt"
+
+	"mydomain.mystuff/mypkg"
+)
+
+const s = fmt.Sprintf("%s", "` + largeString + `")
+const x = mypkg.Sprintf("%s", "my package")
+
+// end
+`
+
+	if got := string(out); got != want {
+		t.Errorf("Process returned unexpected result.\ngot:\n%v\nwant:\n%v", got, want)
+	}
+}
+
+// Ensures a token that is larger that
+// https://golang.org/issues/18201
+func TestProcessTokenTooLarge(t *testing.T) {
+	const largeSize = maxScanTokenSize + 1
+	largeString := strings.Repeat("x", largeSize)
+
+	in := `package testimports
+
+import (
+	"fmt"
+	"mydomain.mystuff/mypkg"
+)
+
+const s = fmt.Sprintf("%s", "` + largeString + `")
+const x = mypkg.Sprintf("%s", "my package")
+
+// end
+`
+
+	_, err := Process("foo", []byte(in), nil)
+
+	if err != bufio.ErrTooLong {
+		t.Errorf("Process did not returned expected error.\n got:\n%v\nwant:\n%v", err, bufio.ErrTooLong)
+	}
+}
diff --git a/imports/imports.go b/imports/imports.go
index 67573f49..d789bb5b 100644
--- a/imports/imports.go
+++ b/imports/imports.go
@@ -98,7 +98,10 @@ func Process(filename string, src []byte, opt *Options) ([]byte, error) {
 		out = adjust(src, out)
 	}
 	if len(spacesBefore) > 0 {
-		out = addImportSpaces(bytes.NewReader(out), spacesBefore)
+		out, err = addImportSpaces(bytes.NewReader(out), spacesBefore)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	out, err = format.Source(out)
@@ -256,9 +259,14 @@ func matchSpace(orig []byte, src []byte) []byte {
 
 var impLine = regexp.MustCompile(`^\s+(?:[\w\.]+\s+)?"(.+)"`)
 
-func addImportSpaces(r io.Reader, breaks []string) []byte {
+// Used to set Scanner buffer size so that large tokens can be handled.
+// see https://github.com/golang/go/issues/18201
+const maxScanTokenSize = bufio.MaxScanTokenSize * 16
+
+func addImportSpaces(r io.Reader, breaks []string) ([]byte, error) {
 	var out bytes.Buffer
 	sc := bufio.NewScanner(r)
+	sc.Buffer(nil, maxScanTokenSize)
 	inImports := false
 	done := false
 	for sc.Scan() {
@@ -285,5 +293,5 @@ func addImportSpaces(r io.Reader, breaks []string) []byte {
 
 		fmt.Fprintln(&out, s)
 	}
-	return out.Bytes()
+	return out.Bytes(), sc.Err()
 }