diff --git a/doc/configuration.txt b/doc/configuration.txt
index d9368b938..4e18f0f6e 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -583,6 +583,8 @@ The following keywords are supported in the "global" section :
    - gid
    - group
    - hard-stop-after
+   - h1-case-adjust
+   - h1-case-adjust-file
    - log
    - log-tag
    - log-send-hostname
@@ -837,6 +839,55 @@ hard-stop-after <time>
     global
       hard-stop-after 30s
 
+h1-case-adjust <from> <to>
+  Defines the case adjustment to apply, when enabled, to the header name
+  <from>, to change it to <to> before sending it to HTTP/1 clients or
+  servers. <from> must be in lower case, and <from> and <to> must not differ
+  except for their case. It may be repeated if several header names need to be
+  ajusted. Duplicate entries are not allowed. If a lot of header names have to
+  be adjusted, it might be more convenient to use "h1-case-adjust-file".
+  Please note that no transformation will be applied unless "option
+  h1-case-adjust-bogus-client" or "option h1-case-adjust-bogus-server" is
+  specified in a proxy.
+
+  There is no standard case for header names because, as stated in RFC7230,
+  they are case-insensitive. So applications must handle them in a case-
+  insensitive manner. But some bogus applications violate the standards and
+  erroneously rely on the cases most commonly used by browsers. This problem
+  becomes critical with HTTP/2 because all header names must be exchanged in
+  lower case, and HAProxy follows the same convention. All header names are
+  sent in lower case to clients and servers, regardless of the HTTP version.
+
+  Applications which fail to properly process requests or responses may require
+  to temporarily use such workarounds to adjust header names sent to them for
+  the time it takes the application to be fixed. Please note that an
+  application which requires such workarounds might be vulnerable to content
+  smuggling attacks and must absolutely be fixed.
+
+  Example:
+    global
+      h1-case-adjust content-length Content-Length
+
+  See "h1-case-adjust-file", "option h1-case-adjust-bogus-client" and
+  "option h1-case-adjust-bogus-server".
+
+h1-case-adjust-file <hdrs-file>
+  Defines a file containing a list of key/value pairs used to adjust the case
+  of some header names before sending them to HTTP/1 clients or servers. The
+  file <hdrs-file> must contain 2 header names per line. The first one must be
+  in lower case and both must not differ except for their case. Lines which
+  start with '#' are ignored, just like empty lines. Leading and trailing tabs
+  and spaces are stripped. Duplicate entries are not allowed. Please note that
+  no transformation will be applied unless "option h1-case-adjust-bogus-client"
+  or "option h1-case-adjust-bogus-server" is specified in a proxy.
+
+  If this directive is repeated, only the last one will be processed.  It is an
+  alternative to the directive "h1-case-adjust" if a lot of header names need
+  to be adjusted. Please read the risks associated with using this.
+
+  See "h1-case-adjust", "option h1-case-adjust-bogus-client" and
+  "option h1-case-adjust-bogus-server".
+
 group <group name>
   Similar to "gid" but uses the GID of group name <group name> from /etc/group.
   See also "gid" and "user".
@@ -2397,6 +2448,8 @@ option dontlog-normal                (*)  X          X         X         -
 option dontlognull                   (*)  X          X         X         -
 -- keyword -------------------------- defaults - frontend - listen -- backend -
 option forwardfor                         X          X         X         X
+option h1-case-adjust-bogus-client   (*)  X          X         X         -
+option h1-case-adjust-bogus-server   (*)  X          -         X         X
 option http-buffer-request           (*)  X          X         X         X
 option http-ignore-probes            (*)  X          X         X         -
 option http-keep-alive               (*)  X          X         X         X
@@ -6045,6 +6098,76 @@ option forwardfor [ except <network> ] [ header <name> ] [ if-none ]
              "option http-keep-alive"
 
 
+option h1-case-adjust-bogus-client
+no option h1-case-adjust-bogus-client
+  Enable or disable the case adjustment of HTTP/1 headers sent to bogus clients
+  May be used in sections :   defaults | frontend | listen | backend
+                                 yes   |    yes   |   yes  |   no
+  Arguments : none
+
+  There is no standard case for header names because, as stated in RFC7230,
+  they are case-insensitive. So applications must handle them in a case-
+  insensitive manner. But some bogus applications violate the standards and
+  erroneously rely on the cases most commonly used by browsers. This problem
+  becomes critical with HTTP/2 because all header names must be exchanged in
+  lower case, and HAProxy follows the same convention. All header names are
+  sent in lower case to clients and servers, regardless of the HTTP version.
+
+  When HAProxy receives an HTTP/1 response, its header names are converted to
+  lower case and manipulated and sent this way to the clients. If a client is
+  known to violate the HTTP standards and to fail to process a response coming
+  from HAProxy, it is possible to transform the lower case header names to a
+  different format when the response is formatted and sent to the client, by
+  enabling this option and specifying the list of headers to be reformatted
+  using the global directives "h1-case-adjust" or "h1-case-adjust-file". This
+  must only be a temporary workaround for the time it takes the client to be
+  fixed, because clients which require such workarounds might be vulnerable to
+  content smuggling attacks and must absolutely be fixed.
+
+  Please note that this option will not affect standards-compliant clients.
+
+  If this option has been enabled in a "defaults" section, it can be disabled
+  in a specific instance by prepending the "no" keyword before it.
+
+  See also: "option h1-case-adjust-bogus-server", "h1-case-adjust",
+  "h1-case-adjust-file".
+
+
+option h1-case-adjust-bogus-server
+no option h1-case-adjust-bogus-server
+  Enable or disable the case adjustment of HTTP/1 headers sent to bogus servers
+  May be used in sections :   defaults | frontend | listen | backend
+                                 yes   |    no   |   yes  |   yes
+  Arguments : none
+
+  There is no standard case for header names because, as stated in RFC7230,
+  they are case-insensitive. So applications must handle them in a case-
+  insensitive manner. But some bogus applications violate the standards and
+  erroneously rely on the cases most commonly used by browsers. This problem
+  becomes critical with HTTP/2 because all header names must be exchanged in
+  lower case, and HAProxy follows the same convention. All header names are
+  sent in lower case to clients and servers, regardless of the HTTP version.
+
+  When HAProxy receives an HTTP/1 request, its header names are converted to
+  lower case and manipulated and sent this way to the servers. If a server is
+  known to violate the HTTP standards and to fail to process a request coming
+  from HAProxy, it is possible to transform the lower case header names to a
+  different format when the request is formatted and sent to the server, by
+  enabling this option and specifying the list of headers to be reformatted
+  using the global directives "h1-case-adjust" or "h1-case-adjust-file". This
+  must only be a temporary workaround for the time it takes the server to be
+  fixed, because servers which require such workarounds might be vulnerable to
+  content smuggling attacks and must absolutely be fixed.
+
+  Please note that this option will not affect standards-compliant servers.
+
+  If this option has been enabled in a "defaults" section, it can be disabled
+  in a specific instance by prepending the "no" keyword before it.
+
+  See also: "option h1-case-adjust-bogus-client", "h1-case-adjust",
+  "h1-case-adjust-file".
+
+
 option http-buffer-request
 no option http-buffer-request
   Enable or disable waiting for whole HTTP request body before proceeding
diff --git a/include/types/proxy.h b/include/types/proxy.h
index a951a77b6..32ce307f8 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -143,7 +143,10 @@ enum PR_SRV_STATE_FILE {
 #define PR_O2_INDEPSTR	0x00001000	/* independent streams, don't update rex on write */
 #define PR_O2_SOCKSTAT	0x00002000	/* collect & provide separate statistics for sockets */
 
-/* unused: 0x00004000 0x00008000 0x00010000 */
+#define PR_O2_H1_ADJ_BUGCLI 0x00008000 /* adjust the case of h1 headers of the response for bogus clients */
+#define PR_O2_H1_ADJ_BUGSRV 0x00004000 /* adjust the case of h1 headers of the request for bogus servers */
+
+/* unused:  0x00010000 */
 
 #define PR_O2_NODELAY   0x00020000      /* fully interactive mode, never delay outgoing data */
 #define PR_O2_USE_PXHDR 0x00040000      /* use Proxy-Connection for proxy requests */
diff --git a/src/mux_h1.c b/src/mux_h1.c
index 659a277d1..f4243a225 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -16,6 +16,8 @@
 #include <common/htx.h>
 #include <common/initcall.h>
 
+#include <ebistree.h>
+
 #include <types/pipe.h>
 #include <types/proxy.h>
 #include <types/session.h>
@@ -106,6 +108,22 @@ struct h1s {
 	uint16_t status;       /* HTTP response status */
 };
 
+/* Map of headers used to convert outgoing headers */
+struct h1_hdrs_map {
+	char *name;
+	struct eb_root map;
+};
+
+/* An entry in a headers map */
+struct h1_hdr_entry  {
+	struct ist name;
+	struct ebpt_node node;
+};
+
+/* Declare the headers map */
+static struct h1_hdrs_map hdrs_map = { .name = NULL, .map  = EB_ROOT };
+
+
 /* the h1c and h1s pools */
 DECLARE_STATIC_POOL(pool_head_h1c, "h1c", sizeof(struct h1c));
 DECLARE_STATIC_POOL(pool_head_h1s, "h1s", sizeof(struct h1s));
@@ -802,6 +820,34 @@ static void h1_process_output_conn_mode(struct h1s *h1s, struct h1m *h1m, struct
 		h1_update_res_conn_value(h1s, h1m, conn_val);
 }
 
+/* Try to adjust the case of the message header name using the global map
+ * <hdrs_map>.
+ */
+static void h1_adjust_case_outgoing_hdr(struct h1s *h1s, struct h1m *h1m, struct ist *name)
+{
+	struct ebpt_node *node;
+	struct h1_hdr_entry *entry;
+
+	/* No entry in the map, do nothing */
+	if (eb_is_empty(&hdrs_map.map))
+		return;
+
+	/* No conversion fo the request headers */
+	if (!(h1m->flags & H1_MF_RESP) && !(h1s->h1c->px->options2 & PR_O2_H1_ADJ_BUGSRV))
+		return;
+
+	/* No conversion fo the response headers */
+	if ((h1m->flags & H1_MF_RESP) && !(h1s->h1c->px->options2 & PR_O2_H1_ADJ_BUGCLI))
+		return;
+
+	node = ebis_lookup_len(&hdrs_map.map, name->ptr, name->len);
+	if (!node)
+		return;
+	entry = container_of(node, struct h1_hdr_entry, node);
+	name->ptr = entry->name.ptr;
+	name->len = entry->name.len;
+}
+
 /* Append the description of what is present in error snapshot <es> into <out>.
  * The description must be small enough to always fit in a buffer. The output
  * buffer may be the trash so the trash must not be used inside this function.
@@ -1646,6 +1692,9 @@ static size_t h1_process_output(struct h1c *h1c, struct buffer *buf, size_t coun
 						goto skip_hdr;
 				}
 
+				/* Try to adjust the case of the header name */
+				if (h1c->px->options2 & (PR_O2_H1_ADJ_BUGCLI|PR_O2_H1_ADJ_BUGSRV))
+					h1_adjust_case_outgoing_hdr(h1s, h1m, &n);
 				if (!htx_hdr_to_h1(n, v, &tmp))
 					goto copy;
 			  skip_hdr:
@@ -1665,6 +1714,9 @@ static size_t h1_process_output(struct h1c *h1c, struct buffer *buf, size_t coun
 					v = ist("");
 					h1_process_output_conn_mode(h1s, h1m, &v);
 					if (v.len) {
+						/* Try to adjust the case of the header name */
+						if (h1c->px->options2 & (PR_O2_H1_ADJ_BUGCLI|PR_O2_H1_ADJ_BUGSRV))
+							h1_adjust_case_outgoing_hdr(h1s, h1m, &n);
 						if (!htx_hdr_to_h1(n, v, &tmp))
 							goto copy;
 					}
@@ -1752,6 +1804,10 @@ static size_t h1_process_output(struct h1c *h1c, struct buffer *buf, size_t coun
 				else { // HTX_BLK_TLR
 					n = htx_get_blk_name(chn_htx, blk);
 					v = htx_get_blk_value(chn_htx, blk);
+
+					/* Try to adjust the case of the header name */
+					if (h1c->px->options2 & (PR_O2_H1_ADJ_BUGCLI|PR_O2_H1_ADJ_BUGSRV))
+						h1_adjust_case_outgoing_hdr(h1s, h1m, &n);
 					if (!htx_hdr_to_h1(n, v, &tmp))
 						goto copy;
 				}
@@ -2512,6 +2568,195 @@ static void h1_show_fd(struct buffer *msg, struct connection *conn)
 	}
 }
 
+
+/* Add an entry in the headers map. Returns -1 on error and 0 on success. */
+static int add_hdr_case_adjust(const char *from, const char *to, char **err)
+{
+	struct h1_hdr_entry *entry;
+
+	/* Be sure there is a non-empty <to> */
+	if (!strlen(to)) {
+		memprintf(err, "expect <to>");
+		return -1;
+	}
+
+	/* Be sure only the case differs between <from> and <to> */
+	if (strcasecmp(from, to)) {
+		memprintf(err, "<from> and <to> must not differ execpt the case");
+		return -1;
+	}
+
+	/* Be sure <from> does not already existsin the tree */
+	if (ebis_lookup(&hdrs_map.map, from)) {
+		memprintf(err, "duplicate entry '%s'", from);
+		return -1;
+	}
+
+	/* Create the entry and insert it in the tree */
+	entry = malloc(sizeof(*entry));
+	if (!entry) {
+		memprintf(err, "out of memory");
+		return -1;
+	}
+
+	entry->node.key = strdup(from);
+	entry->name.ptr = strdup(to);
+	entry->name.len = strlen(to);
+	if (!entry->node.key || !entry->name.ptr) {
+		free(entry->node.key);
+		free(entry->name.ptr);
+		free(entry);
+		memprintf(err, "out of memory");
+		return -1;
+	}
+	ebis_insert(&hdrs_map.map, &entry->node);
+	return 0;
+}
+
+static void h1_hdeaders_case_adjust_deinit()
+{
+	struct ebpt_node *node, *next;
+	struct h1_hdr_entry *entry;
+
+	node = ebpt_first(&hdrs_map.map);
+	while (node) {
+		next = ebpt_next(node);
+		ebpt_delete(node);
+		entry = container_of(node, struct h1_hdr_entry, node);
+		free(entry->node.key);
+		free(entry->name.ptr);
+		free(entry);
+		node = next;
+	}
+	free(hdrs_map.name);
+}
+
+static int cfg_h1_headers_case_adjust_postparser()
+{
+	FILE *file = NULL;
+	char *c, *key_beg, *key_end, *value_beg, *value_end;
+	char *err;
+	int rc, line = 0, err_code = 0;
+
+	if (!hdrs_map.name)
+		goto end;
+
+	file = fopen(hdrs_map.name, "r");
+	if (!file) {
+		ha_alert("config : h1-outgoing-headers-case-adjust-file '%s': failed to open file.\n",
+			 hdrs_map.name);
+                err_code |= ERR_ALERT | ERR_FATAL;
+		goto end;
+	}
+
+	/* now parse all lines. The file may contain only two header name per
+	 * line, separated by spaces. All heading and trailing spaces will be
+	 * ignored. Lines starting with a # are ignored.
+	 */
+	while (fgets(trash.area, trash.size, file) != NULL) {
+		line++;
+		c = trash.area;
+
+		/* strip leading spaces and tabs */
+		while (*c == ' ' || *c == '\t')
+			c++;
+
+		/* ignore emptu lines, or lines beginning with a dash */
+		if (*c == '#' || *c == '\0' || *c == '\r' || *c == '\n')
+			continue;
+
+		/* look for the end of the key */
+		key_beg = c;
+		while (*c != '\0' && *c != ' ' && *c != '\t' && *c != '\n' && *c != '\r')
+			c++;
+		key_end = c;
+
+		/* strip middle spaces and tabs */
+		while (*c == ' ' || *c == '\t')
+			c++;
+
+		/* look for the end of the value, it is the end of the line */
+		value_beg = c;
+		while (*c && *c != '\n' && *c != '\r')
+			c++;
+		value_end = c;
+
+		/* trim possibly trailing spaces and tabs */
+		while (value_end > value_beg && (value_end[-1] == ' ' || value_end[-1] == '\t'))
+			value_end--;
+
+		/* set final \0 and check entries */
+		*key_end = '\0';
+		*value_end = '\0';
+
+		err = NULL;
+		rc = add_hdr_case_adjust(key_beg, value_beg, &err);
+		if (rc < 0) {
+			free(err);
+			ha_alert("config : h1-outgoing-headers-case-adjust-file '%s' : %s at line %d.\n",
+				 hdrs_map.name, err, line);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto end;
+		}
+		if (rc > 0) {
+			free(err);
+			ha_warning("config : h1-outgoing-headers-case-adjust-file '%s' : %s at line %d.\n",
+				   hdrs_map.name, err, line);
+			err_code |= ERR_WARN;
+		}
+	}
+
+  end:
+	if (file)
+		fclose(file);
+	hap_register_post_deinit(h1_hdeaders_case_adjust_deinit);
+	return err_code;
+}
+
+
+/* config parser for global "h1-outgoing-header-case-adjust" */
+static int cfg_parse_h1_header_case_adjust(char **args, int section_type, struct proxy *curpx,
+					   struct proxy *defpx, const char *file, int line,
+					   char **err)
+{
+        if (too_many_args(2, args, err, NULL))
+                return -1;
+        if (!*(args[1]) || !*(args[2])) {
+                memprintf(err, "'%s' expects <from> and <to> as argument.", args[0]);
+		return -1;
+	}
+	return add_hdr_case_adjust(args[1], args[2], err);
+}
+
+/* config parser for global "h1-outgoing-headers-case-adjust-file" */
+static int cfg_parse_h1_headers_case_adjust_file(char **args, int section_type, struct proxy *curpx,
+						 struct proxy *defpx, const char *file, int line,
+						 char **err)
+{
+        if (too_many_args(1, args, err, NULL))
+                return -1;
+        if (!*(args[1])) {
+                memprintf(err, "'%s' expects <file> as argument.", args[0]);
+		return -1;
+	}
+	free(hdrs_map.name);
+	hdrs_map.name = strdup(args[1]);
+        return 0;
+}
+
+
+/* config keyword parsers */
+static struct cfg_kw_list cfg_kws = {{ }, {
+		{ CFG_GLOBAL, "h1-case-adjust", cfg_parse_h1_header_case_adjust },
+		{ CFG_GLOBAL, "h1-case-adjust-file", cfg_parse_h1_headers_case_adjust_file },
+		{ 0, NULL, NULL },
+	}
+};
+
+INITCALL1(STG_REGISTER, cfg_register_keywords, &cfg_kws);
+REGISTER_CONFIG_POSTPARSER("h1-headers-map", cfg_h1_headers_case_adjust_postparser);
+
+
 /****************************************/
 /* MUX initialization and instanciation */
 /****************************************/
diff --git a/src/proxy.c b/src/proxy.c
index 48c115f1c..a6cd697d0 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -110,6 +110,9 @@ const struct cfg_opt cfg_opts2[] =
 	{ "http-pretend-keepalive",       PR_O2_FAKE_KA,   PR_CAP_BE, 0, PR_MODE_HTTP },
 	{ "http-no-delay",                PR_O2_NODELAY,   PR_CAP_FE|PR_CAP_BE, 0, PR_MODE_HTTP },
 	{ "http-use-htx",                 0,               PR_CAP_FE|PR_CAP_BE, 0, 0 }, // deprecated
+
+	{"h1-case-adjust-bogus-client",   PR_O2_H1_ADJ_BUGCLI, PR_CAP_FE, 0, PR_MODE_HTTP },
+	{"h1-case-adjust-bogus-server",   PR_O2_H1_ADJ_BUGSRV, PR_CAP_BE, 0, PR_MODE_HTTP },
 	{ NULL, 0, 0, 0 }
 };