diff --git a/zio/csvio/preprocess.go b/zio/csvio/preprocess.go
index dca3fd0b15..140dbd0f88 100644
--- a/zio/csvio/preprocess.go
+++ b/zio/csvio/preprocess.go
@@ -79,7 +79,7 @@ func (p *preprocess) parseField() ([]byte, error) {
 			ending := []byte{c}
 			if hasstr {
 				// If field had quotes wrap entire field in quotes.
-				if last := len(p.scratch) - 1; p.scratch[last] == '\r' {
+				if last := len(p.scratch) - 1; last > 0 && p.scratch[last] == '\r' {
 					ending = []byte("\r\n")
 					p.scratch = p.scratch[:last]
 				}
diff --git a/zio/csvio/preprocess_test.go b/zio/csvio/preprocess_test.go
index 84638390e9..444686cda7 100644
--- a/zio/csvio/preprocess_test.go
+++ b/zio/csvio/preprocess_test.go
@@ -12,12 +12,18 @@ import (
 
 func TestPreprocess(t *testing.T) {
 	const input = `
+,,
+"","",""
+"""","""",""""
 field1,"field"2,field"3" my friend
 field4,"field"5 with "multiple" quotes "to" escape,field6
 """,""",""" has a couple "" embedded quotes and a , comma",""" """
 x,"hello,
 "" world , " foo,y`
 	const expected = `
+,,
+"","",""
+"""","""",""""
 field1,"field2","field3 my friend"
 field4,"field5 with multiple quotes to escape",field6
 """,""",""" has a couple "" embedded quotes and a , comma",""" """