diff --git a/gitdiff/file_header.go b/gitdiff/file_header.go
index e3185bd..58904b4 100644
--- a/gitdiff/file_header.go
+++ b/gitdiff/file_header.go
@@ -527,7 +527,7 @@ func hasEpochTimestamp(s string) bool {
 
 	// a valid timestamp can have optional ':' in zone specifier
 	// remove that if it exists so we have a single format
-	if ts[len(ts)-3] == ':' {
+	if len(ts) >= 3 && ts[len(ts)-3] == ':' {
 		ts = ts[:len(ts)-3] + ts[len(ts)-2:]
 	}
 
diff --git a/gitdiff/file_header_test.go b/gitdiff/file_header_test.go
index 99cfed3..102795c 100644
--- a/gitdiff/file_header_test.go
+++ b/gitdiff/file_header_test.go
@@ -724,6 +724,14 @@ func TestHasEpochTimestamp(t *testing.T) {
 			Input:  "+++ file.txt\t2019-03-21 12:34:56.789 -0700\n",
 			Output: false,
 		},
+		"notTimestamp": {
+			Input:  "+++ file.txt\trandom text\n",
+			Output: false,
+		},
+		"notTimestampShort": {
+			Input:  "+++ file.txt\t0\n",
+			Output: false,
+		},
 	}
 
 	for name, test := range tests {