diff --git a/src/parser.rs b/src/parser.rs
index d8adb37..069bd2d 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -1,4 +1,4 @@
-use std::collections::{btree_map, hash_map, BTreeMap};
+use std::collections::{btree_map, hash_map, BTreeMap, HashSet};
 use std::fmt;
 use std::fs::File;
 use std::io::{self, BufRead, BufReader, Read};
@@ -6,6 +6,8 @@ use std::num::ParseIntError;
 use std::path::Path;
 use std::str;
 
+use log::error;
+
 use xml::events::{BytesStart, Event};
 use xml::Reader;
 
@@ -125,6 +127,8 @@ pub fn parse_lcov<T: Read>(
     let mut cur_lines = BTreeMap::new();
     let mut cur_branches = BTreeMap::new();
     let mut cur_functions = FxHashMap::default();
+    // Only needed for the workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=1597997.
+    let mut cur_fndas = HashSet::new();
 
     let mut results = Vec::new();
 
@@ -182,9 +186,24 @@ pub fn parse_lcov<T: Read>(
                 "FN" => {
                     let mut f_splits = value.splitn(2, ',');
                     let start = try_parse_next!(f_splits, l);
-                    let f_name = try_next!(f_splits, l);
+                    let mut f_name = try_next!(f_splits, l).to_owned();
+
+                    // Workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=1597997.
+                    if f_name == "top-level" {
+                        let mut i = 1;
+
+                        while cur_functions.contains_key(&f_name) {
+                            if i == 1 {
+                                error!("{} FN duplicated in a lcov file", f_name);
+                            }
+
+                            f_name = format!("top-level{}", i);
+                            i += 1;
+                        }
+                    }
+
                     cur_functions.insert(
-                        f_name.to_owned(),
+                        f_name,
                         Function {
                             start,
                             executed: false,
@@ -194,8 +213,28 @@ pub fn parse_lcov<T: Read>(
                 "FNDA" => {
                     let mut f_splits = value.splitn(2, ',');
                     let executed = try_next!(f_splits, l) != "0";
-                    let f_name = try_next!(f_splits, l);
-                    if let Some(f) = cur_functions.get_mut(f_name) {
+                    let mut f_name = try_next!(f_splits, l).to_owned();
+
+                    // Workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=1597997.
+                    let mut is_top_level = false;
+                    if f_name == "top-level" {
+                        is_top_level = true;
+
+                        let mut i = 1;
+
+                        while cur_fndas.contains(&f_name) {
+                            let new_f_name = format!("top-level{}", i);
+                            i += 1;
+
+                            if cur_functions.contains_key(&new_f_name) {
+                                f_name = new_f_name;
+                            } else {
+                                break;
+                            }
+                        }
+                    }
+
+                    if let Some(f) = cur_functions.get_mut(&f_name) {
                         f.executed |= executed;
                     } else {
                         return Err(ParserError::Parse(format!(
@@ -203,6 +242,10 @@ pub fn parse_lcov<T: Read>(
                             f_name
                         )));
                     }
+
+                    if is_top_level {
+                        cur_fndas.insert(f_name);
+                    }
                 }
                 "BRDA" => {
                     if branch_enabled {
@@ -964,6 +1007,288 @@ mod tests {
         assert!(result.is_err());
     }
 
+    // Test for the workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=1597997.
+    #[test]
+    fn test_lcov_parser_duplicate_fn_fnda() {
+        let f = File::open("./test/duplicate_fn_fnda.info").expect("Failed to open lcov file");
+        let file = BufReader::new(&f);
+        let results = parse_lcov(file, true).unwrap();
+
+        assert_eq!(results.len(), 1);
+
+        let (ref source_name, ref result) = results[0];
+        assert_eq!(
+            source_name,
+            "devtools/client/webconsole/components/Output/ConsoleTable.js"
+        );
+        assert_eq!(
+            result.lines,
+            [
+                (9, 1),
+                (10, 1),
+                (11, 1),
+                (16, 1),
+                (17, 1),
+                (18, 1),
+                (21, 2),
+                (22, 1),
+                (25, 2),
+                (26, 1),
+                (27, 1),
+                (28, 1),
+                (31, 1),
+                (33, 1),
+                (35, 1),
+                (36, 1),
+                (37, 0),
+                (38, 0),
+                (39, 0),
+                (40, 0),
+                (41, 0),
+                (43, 0),
+                (48, 2),
+                (49, 2),
+                (50, 2),
+                (54, 3),
+                (55, 2),
+                (57, 2),
+                (58, 2),
+                (59, 0),
+                (63, 2),
+                (64, 2),
+                (65, 2),
+                (66, 0),
+                (68, 2),
+                (69, 2),
+                (73, 0),
+                (74, 0),
+                (75, 0),
+                (76, 0),
+                (77, 0),
+                (80, 2),
+                (82, 3),
+                (83, 2),
+                (84, 2),
+                (85, 12),
+                (86, 12),
+                (87, 6),
+                (88, 6),
+                (89, 6),
+                (90, 6),
+                (91, 6),
+                (93, 6),
+                (97, 2),
+                (98, 2),
+                (100, 3),
+                (101, 2),
+                (103, 6),
+                (104, 4),
+                (105, 4),
+                (107, 16),
+                (108, 12),
+                (110, 12),
+                (111, 4),
+                (112, 16),
+                (113, 8),
+                (114, 8),
+                (115, 8),
+                (116, 8),
+                (117, 8),
+                (120, 24),
+                (121, 24),
+                (122, 12),
+                (123, 12),
+                (124, 12),
+                (125, 12),
+                (127, 12),
+                (131, 4),
+                (132, 4),
+                (133, 2),
+                (135, 3),
+                (136, 2),
+                (137, 2),
+                (140, 2),
+                (143, 2),
+                (144, 2),
+                (145, 0),
+                (148, 2),
+                (149, 0),
+                (152, 2),
+                (156, 2),
+                (157, 2),
+                (158, 0),
+                (160, 4),
+                (161, 2),
+                (162, 2),
+                (163, 2),
+                (164, 2),
+                (165, 2),
+                (166, 2),
+                (167, 2),
+                (170, 2),
+                (171, 2),
+                (173, 2),
+                (176, 2),
+                (177, 2),
+                (180, 2),
+                (181, 0),
+                (182, 2),
+                (185, 2),
+                (187, 2),
+                (188, 2),
+                (190, 2),
+                (191, 2),
+                (192, 0),
+                (194, 2),
+                (195, 2),
+                (196, 0),
+                (198, 2),
+                (199, 2),
+                (200, 2),
+                (202, 1),
+                (203, 1),
+                (206, 2),
+                (207, 2),
+                (208, 2),
+                (209, 2),
+                (210, 2),
+                (211, 0),
+                (212, 2),
+                (213, 2),
+                (219, 2),
+                (220, 0),
+                (221, 0),
+                (226, 2),
+                (227, 2),
+                (229, 2),
+                (230, 2),
+                (232, 2),
+                (233, 4),
+                (234, 12),
+                (237, 2),
+                (239, 10),
+                (240, 8),
+                (241, 8),
+                (244, 8),
+                (245, 6),
+                (246, 6),
+                (247, 0),
+                (248, 0),
+                (250, 6),
+                (254, 2),
+                (255, 4),
+                (256, 4),
+                (259, 4),
+                (260, 4),
+                (263, 4),
+                (265, 4),
+                (266, 2),
+                (267, 2),
+                (269, 4),
+                (270, 2),
+                (271, 2),
+                (272, 2),
+                (275, 2),
+                (276, 2),
+                (277, 0),
+                (279, 0),
+                (280, 0),
+                (282, 2),
+                (285, 4),
+                (287, 4),
+                (288, 0),
+                (294, 2),
+                (295, 0),
+                (299, 2),
+                (300, 2),
+                (301, 2),
+                (302, 2),
+                (306, 2),
+                (307, 2),
+                (308, 2),
+                (309, 2),
+                (312, 2),
+                (313, 2),
+                (314, 2),
+                (316, 2),
+                (322, 0),
+                (323, 0),
+                (325, 0),
+                (326, 0),
+                (328, 0),
+                (329, 0),
+                (330, 0),
+                (333, 0),
+                (335, 0),
+                (336, 0),
+                (337, 0),
+                (340, 0),
+                (341, 0),
+                (342, 0),
+                (343, 0),
+                (344, 0),
+                (346, 0),
+                (350, 0),
+                (351, 0),
+                (352, 0),
+                (355, 0),
+                (356, 0),
+                (359, 0),
+                (361, 0),
+                (363, 0),
+                (364, 0),
+                (365, 0),
+                (366, 0),
+                (367, 0),
+                (368, 0),
+                (369, 0),
+                (370, 0),
+                (371, 0),
+                (374, 0),
+                (375, 0),
+                (378, 0),
+                (379, 0),
+                (380, 0),
+                (382, 0),
+                (383, 0),
+                (386, 0),
+                (389, 0),
+                (391, 0),
+                (392, 0),
+                (398, 0),
+                (399, 0),
+                (403, 0),
+                (404, 0),
+                (405, 0),
+                (406, 0),
+                (410, 0),
+                (411, 0),
+                (412, 0),
+                (413, 0),
+                (416, 0),
+                (417, 0),
+                (418, 0),
+                (420, 0),
+                (422, 1),
+            ]
+            .iter()
+            .cloned()
+            .collect()
+        );
+        assert!(result.functions.contains_key("top-level"));
+        let func = result.functions.get("top-level").unwrap();
+        assert_eq!(func.start, 1);
+        assert_eq!(func.executed, true);
+        assert!(result.functions.contains_key("top-level1"));
+        let func = result.functions.get("top-level1").unwrap();
+        assert_eq!(func.start, 17);
+        assert_eq!(func.executed, true);
+        assert!(result.functions.contains_key("top-level2"));
+        let func = result.functions.get("top-level2").unwrap();
+        assert_eq!(func.start, 176);
+        assert_eq!(func.executed, true);
+    }
+
     #[test]
     fn test_parser() {
         let results = parse_gcov(Path::new("./test/prova.gcov")).unwrap();
diff --git a/src/producer.rs b/src/producer.rs
index 259efba..a8fc2aa 100644
--- a/src/producer.rs
+++ b/src/producer.rs
@@ -655,6 +655,7 @@ mod tests {
             (ItemFormat::INFO, false, "prova_fn_with_commas.info", false),
             (ItemFormat::INFO, false, "empty_line.info", false),
             (ItemFormat::INFO, false, "invalid_DA_record.info", false),
+            (ItemFormat::INFO, false, "duplicate_fn_fnda.info", false),
             (
                 ItemFormat::INFO,
                 false,
diff --git a/test/duplicate_fn_fnda.info b/test/duplicate_fn_fnda.info
new file mode 100644
index 0000000..5d7d161
--- /dev/null
+++ b/test/duplicate_fn_fnda.info
@@ -0,0 +1,298 @@
+SF:devtools/client/webconsole/components/Output/ConsoleTable.js
+FN:1,top-level
+FN:17,top-level
+FN:176,top-level
+FN:190,top-level
+FN:205,top-level
+FN:217,top-level
+FN:221,top-level
+FN:226,top-level
+FN:232,top-level
+FN:234,top-level
+FN:239,top-level
+FN:295,top-level
+FN:322,top-level
+FN:328,top-level
+FN:330,top-level
+FN:335,top-level
+FN:399,top-level
+FN:47,top-level
+FN:36,top-level
+FN:54,top-level
+FN:82,top-level
+FN:84,top-level
+FN:100,top-level
+FN:103,top-level
+FN:107,top-level
+FN:135,top-level
+FNDA:1,top-level
+FNDA:1,top-level
+FNDA:2,top-level
+FNDA:2,top-level
+FNDA:2,top-level
+FNDA:2,top-level
+FNDA:2,top-level
+FNDA:4,top-level
+FNDA:8,top-level
+FNDA:8,top-level
+FNDA:2,top-level
+FNDA:2,top-level
+FNDA:2,top-level
+FNDA:6,top-level
+FNDA:2,top-level
+FNDA:4,top-level
+FNDA:12,top-level
+FNDA:2,top-level
+FNF:26
+FNH:18
+BRF:248
+BRH:79
+DA:9,1
+DA:10,1
+DA:11,1
+DA:16,1
+DA:17,1
+DA:18,1
+DA:21,2
+DA:22,1
+DA:25,2
+DA:26,1
+DA:27,1
+DA:28,1
+DA:31,1
+DA:33,1
+DA:35,1
+DA:36,1
+DA:37,0
+DA:38,0
+DA:39,0
+DA:40,0
+DA:41,0
+DA:43,0
+DA:48,2
+DA:49,2
+DA:50,2
+DA:54,3
+DA:55,2
+DA:57,2
+DA:58,2
+DA:59,0
+DA:63,2
+DA:64,2
+DA:65,2
+DA:66,0
+DA:68,2
+DA:69,2
+DA:73,0
+DA:74,0
+DA:75,0
+DA:76,0
+DA:77,0
+DA:80,2
+DA:82,3
+DA:83,2
+DA:84,2
+DA:85,12
+DA:86,12
+DA:87,6
+DA:88,6
+DA:89,6
+DA:90,6
+DA:91,6
+DA:93,6
+DA:97,2
+DA:98,2
+DA:100,3
+DA:101,2
+DA:103,6
+DA:104,4
+DA:105,4
+DA:107,16
+DA:108,12
+DA:110,12
+DA:111,4
+DA:112,16
+DA:113,8
+DA:114,8
+DA:115,8
+DA:116,8
+DA:117,8
+DA:120,24
+DA:121,24
+DA:122,12
+DA:123,12
+DA:124,12
+DA:125,12
+DA:127,12
+DA:131,4
+DA:132,4
+DA:133,2
+DA:135,3
+DA:136,2
+DA:137,2
+DA:140,2
+DA:143,2
+DA:144,2
+DA:145,0
+DA:148,2
+DA:149,0
+DA:152,2
+DA:156,2
+DA:157,2
+DA:158,0
+DA:160,4
+DA:161,2
+DA:162,2
+DA:163,2
+DA:164,2
+DA:165,2
+DA:166,2
+DA:167,2
+DA:170,2
+DA:171,2
+DA:173,2
+DA:176,2
+DA:177,2
+DA:180,2
+DA:181,0
+DA:182,2
+DA:185,2
+DA:187,2
+DA:188,2
+DA:190,2
+DA:191,2
+DA:192,0
+DA:194,2
+DA:195,2
+DA:196,0
+DA:198,2
+DA:199,2
+DA:200,2
+DA:202,1
+DA:203,1
+DA:206,2
+DA:207,2
+DA:208,2
+DA:209,2
+DA:210,2
+DA:211,0
+DA:212,2
+DA:213,2
+DA:219,2
+DA:220,0
+DA:221,0
+DA:226,2
+DA:227,2
+DA:229,2
+DA:230,2
+DA:232,2
+DA:233,4
+DA:234,12
+DA:237,2
+DA:239,10
+DA:240,8
+DA:241,8
+DA:244,8
+DA:245,6
+DA:246,6
+DA:247,0
+DA:248,0
+DA:250,6
+DA:254,2
+DA:255,4
+DA:256,4
+DA:259,4
+DA:260,4
+DA:263,4
+DA:265,4
+DA:266,2
+DA:267,2
+DA:269,4
+DA:270,2
+DA:271,2
+DA:272,2
+DA:275,2
+DA:276,2
+DA:277,0
+DA:279,0
+DA:280,0
+DA:282,2
+DA:285,4
+DA:287,4
+DA:288,0
+DA:294,2
+DA:295,0
+DA:299,2
+DA:300,2
+DA:301,2
+DA:302,2
+DA:306,2
+DA:307,2
+DA:308,2
+DA:309,2
+DA:312,2
+DA:313,2
+DA:314,2
+DA:316,2
+DA:322,0
+DA:323,0
+DA:325,0
+DA:326,0
+DA:328,0
+DA:329,0
+DA:330,0
+DA:333,0
+DA:335,0
+DA:336,0
+DA:337,0
+DA:340,0
+DA:341,0
+DA:342,0
+DA:343,0
+DA:344,0
+DA:346,0
+DA:350,0
+DA:351,0
+DA:352,0
+DA:355,0
+DA:356,0
+DA:359,0
+DA:361,0
+DA:363,0
+DA:364,0
+DA:365,0
+DA:366,0
+DA:367,0
+DA:368,0
+DA:369,0
+DA:370,0
+DA:371,0
+DA:374,0
+DA:375,0
+DA:378,0
+DA:379,0
+DA:380,0
+DA:382,0
+DA:383,0
+DA:386,0
+DA:389,0
+DA:391,0
+DA:392,0
+DA:398,0
+DA:399,0
+DA:403,0
+DA:404,0
+DA:405,0
+DA:406,0
+DA:410,0
+DA:411,0
+DA:412,0
+DA:413,0
+DA:416,0
+DA:417,0
+DA:418,0
+DA:420,0
+DA:422,1
+LF:246
+LH:159
+end_of_record