diff --git a/src/lib_ccx/ccx_encoders_webvtt.c b/src/lib_ccx/ccx_encoders_webvtt.c
index f62c2204..d5460634 100644
--- a/src/lib_ccx/ccx_encoders_webvtt.c
+++ b/src/lib_ccx/ccx_encoders_webvtt.c
@@ -115,7 +115,7 @@ static const char *webvtt_inline_css = "/* default values */\n"
 		"  background-color: rgba(0, 0, 0, 0.5);\n"
 		"}";
 
-static const char** webvtt_pac_row_percent[] = { "10", "15.33", "20.66", "26", "31.33", "36.66", "42",
+static const char* webvtt_pac_row_percent[] = { "10", "15.33", "20.66", "26", "31.33", "36.66", "42",
 		"47.33", "52.66", "58", "63.33", "68.66", "74", "79.33", "84.66" };
 
 /* The timing here is not PTS based, but output based, i.e. user delay must be accounted for
@@ -219,7 +219,7 @@ int write_webvtt_header(struct encoder_ctx *context)
 			mprint("Warning: Error creating the file %s\n", css_file_name);
 			return -1;
 		}
-		fprintf(f, webvtt_inline_css);
+		fprintf(f, "%s",webvtt_inline_css);
 		fclose(f);
 
 		char* outline_css_file = (char*)malloc((strlen(css_file_name) + strlen(webvtt_outline_css)) * sizeof(char));
diff --git a/src/lib_ccx/matroska.c b/src/lib_ccx/matroska.c
index 328c8841..f1e324aa 100644
--- a/src/lib_ccx/matroska.c
+++ b/src/lib_ccx/matroska.c
@@ -420,9 +420,9 @@ void parse_segment_cluster_block_group(struct matroska_ctx* mkv_ctx, ULLONG clus
             sentence_list[i]->time_end = sentence_list[i]->time_start + block_duration;
 
         if (ccx_options.gui_mode_reports) {
-            ULLONG h1, m1, s1, ms1;
+            unsigned h1, m1, s1, ms1;
             millis_to_time(sentence_list[i]->time_start, &h1, &m1, &s1, &ms1);
-            ULLONG h2, m2, s2, ms2;
+            unsigned h2, m2, s2, ms2;
             millis_to_time(sentence_list[i]->time_end, &h2, &m2, &s2, &ms2);
 
             char *text = sentence_list[i]->text;
@@ -996,7 +996,7 @@ void matroska_save_all(struct matroska_ctx* mkv_ctx,char* lang)
   char* match;
     for (int i = 0; i < mkv_ctx->sub_tracks_count; i++){
       if (lang){
-        if (match = strstr(lang,mkv_ctx->sub_tracks[i]->lang) != NULL)
+        if ((match = strstr(lang,mkv_ctx->sub_tracks[i]->lang)) != NULL)
           save_sub_track(mkv_ctx, mkv_ctx->sub_tracks[i]);
                 }
       else
diff --git a/src/lib_ccx/utility.h b/src/lib_ccx/utility.h
index 78000aa3..656ceaae 100644
--- a/src/lib_ccx/utility.h
+++ b/src/lib_ccx/utility.h
@@ -36,6 +36,7 @@ char *str_reallocncat(char *dst, char *src);
 
 void dump (LLONG mask, unsigned char *start, int l, unsigned long abs_start, unsigned clear_high_bit);
 LLONG change_timebase(LLONG val, struct ccx_rational cur_tb, struct ccx_rational dest_tb);
+void timestamp_to_vtttime(uint64_t timestamp, char *buffer);
 #ifdef _WIN32
 char *strndup(const char *s, size_t n);
 char *strtok_r(char *str, const char *delim, char **saveptr);
diff --git a/src/zlib/gzguts.h b/src/zlib/gzguts.h
index 990a4d25..24c6566c 100644
--- a/src/zlib/gzguts.h
+++ b/src/zlib/gzguts.h
@@ -19,6 +19,7 @@
 #endif
 
 #include <stdio.h>
+#include <unistd.h>
 #include "zlib.h"
 #ifdef STDC
 #  include <string.h>