diff --git a/doc/configuration.txt b/doc/configuration.txt
index 55e56be5f7..00532a895a 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -3114,8 +3114,7 @@ compression offload
     * The response contains a "Content-Encoding" header, indicating that the
       response is already compressed (see compression offload)
 
-  Note: The compression does not rewrite Etag headers, and does not emit the
-        Warning header.
+  Note: The compression does not emit the Warning header.
 
   Examples :
         compression algo gzip
diff --git a/reg-tests/compression/h00001.vtc b/reg-tests/compression/h00001.vtc
new file mode 100644
index 0000000000..0cae679592
--- /dev/null
+++ b/reg-tests/compression/h00001.vtc
@@ -0,0 +1,226 @@
+varnishtest "Compression converts strong ETags to weak ETags"
+
+#REQUIRE_VERSION=1.9
+#REQUIRE_OPTION=ZLIB|SLZ
+
+feature ignore_unknown_macro
+
+server s1 {
+        rxreq
+        expect req.url == "/strong"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: \"123\"" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/weak"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: W/\"456\"" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/weak-incorrect-quoting"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: \"W/789\"" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/empty-strong"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: \"\"" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/empty-weak"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: W/\"\"" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/invalid1"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: \"invalid" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/invalid2"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: invalid\"" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/invalid3"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: invalid" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/invalid4"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: W/\"invalid" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/invalid5"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: W/invalid\"" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/invalid6"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: W/invalid" \
+          -bodylen 100
+
+        rxreq
+        expect req.url == "/multiple"
+        expect req.http.accept-encoding == "gzip"
+        txresp \
+          -hdr "Content-Type: text/plain" \
+          -hdr "ETag: \"one\"" \
+          -hdr "ETag: \"two\"" \
+          -bodylen 100
+} -start
+
+
+haproxy h1 -conf {
+    defaults
+        mode http
+        ${no-htx} option http-use-htx
+        timeout connect 1s
+        timeout client  1s
+        timeout server  1s
+
+    frontend fe-gzip
+        bind "fd@${fe_gzip}"
+        default_backend be-gzip
+
+    backend be-gzip
+        compression algo gzip
+        compression type text/html text/plain
+        server www ${s1_addr}:${s1_port}
+} -start
+
+client c1 -connect ${h1_fe_gzip_sock} {
+        txreq -url "/strong" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "gzip"
+        expect resp.http.etag == "W/\"123\""
+        gunzip
+        expect resp.bodylen == 100
+
+        txreq -url "/weak" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "gzip"
+        expect resp.http.etag == "W/\"456\""
+        gunzip
+        expect resp.bodylen == 100
+
+        txreq -url "/weak-incorrect-quoting" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "gzip"
+        expect resp.http.etag == "W/\"W/789\""
+        gunzip
+        expect resp.bodylen == 100
+
+        txreq -url "/empty-strong" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "gzip"
+        expect resp.http.etag == "W/\"\""
+        gunzip
+        expect resp.bodylen == 100
+
+        txreq -url "/empty-weak" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "gzip"
+        expect resp.http.etag == "W/\"\""
+        gunzip
+        expect resp.bodylen == 100
+
+        txreq -url "/invalid1" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "<undef>"
+        expect resp.http.etag == "\"invalid"
+        expect resp.bodylen == 100
+
+        txreq -url "/invalid2" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "<undef>"
+        expect resp.http.etag == "invalid\""
+        expect resp.bodylen == 100
+
+        txreq -url "/invalid3" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "<undef>"
+        expect resp.http.etag == "invalid"
+        expect resp.bodylen == 100
+
+        txreq -url "/invalid4" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "<undef>"
+        expect resp.http.etag == "W/\"invalid"
+        expect resp.bodylen == 100
+
+        txreq -url "/invalid5" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "<undef>"
+        expect resp.http.etag == "W/invalid\""
+        expect resp.bodylen == 100
+
+        txreq -url "/invalid6" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "<undef>"
+        expect resp.http.etag == "W/invalid"
+        expect resp.bodylen == 100
+
+        txreq -url "/multiple" \
+          -hdr "Accept-Encoding: gzip"
+        rxresp
+        expect resp.status == 200
+        expect resp.http.content-encoding == "<undef>"
+        expect resp.bodylen == 100
+} -run
diff --git a/src/flt_http_comp.c b/src/flt_http_comp.c
index f8fbf4c9d2..cfe864e35a 100644
--- a/src/flt_http_comp.c
+++ b/src/flt_http_comp.c
@@ -466,6 +466,7 @@ static int
 http_set_comp_reshdr(struct comp_state *st, struct stream *s, struct http_msg *msg)
 {
 	struct http_txn *txn = s->txn;
+	struct hdr_ctx ctx;
 
 	/*
 	 * Add Content-Encoding header when it's not identity encoding.
@@ -486,8 +487,6 @@ http_set_comp_reshdr(struct comp_state *st, struct stream *s, struct http_msg *m
 
 	/* remove Content-Length header */
 	if (msg->flags & HTTP_MSGF_CNT_LEN) {
-		struct hdr_ctx ctx;
-
 		ctx.idx = 0;
 		while (http_find_header2("Content-Length", 14, ci_head(&s->res), &txn->hdr_idx, &ctx))
 			http_remove_header2(msg, &txn->hdr_idx, &ctx);
@@ -499,6 +498,22 @@ http_set_comp_reshdr(struct comp_state *st, struct stream *s, struct http_msg *m
 			goto error;
 	}
 
+	ctx.idx = 0;
+	if (http_find_full_header2("ETag", 4, ci_head(&s->res), &txn->hdr_idx, &ctx)) {
+		if (ctx.line[ctx.val] == '"') {
+			/* This a strong ETag. Convert it to a weak one. */
+			trash.data = 8;
+			if (trash.data + ctx.vlen > trash.size)
+				goto error;
+			memcpy(trash.area, "ETag: W/", trash.data);
+			memcpy(trash.area + trash.data, ctx.line + ctx.val, ctx.vlen);
+			trash.data += ctx.vlen;
+			trash.area[trash.data] = '\0';
+			http_remove_header2(msg, &txn->hdr_idx, &ctx);
+			if (http_header_add_tail2(msg, &txn->hdr_idx, trash.area, trash.data) < 0)
+				goto error;
+		}
+	}
 
 	return 1;
 
@@ -512,6 +527,7 @@ static int
 htx_set_comp_reshdr(struct comp_state *st, struct stream *s, struct http_msg *msg)
 {
 	struct htx *htx = htxbuf(&msg->chn->buf);
+	struct http_hdr_ctx ctx;
 
 	/*
 	 * Add Content-Encoding header when it's not identity encoding.
@@ -528,8 +544,6 @@ htx_set_comp_reshdr(struct comp_state *st, struct stream *s, struct http_msg *ms
 
 	/* remove Content-Length header */
 	if (msg->flags & HTTP_MSGF_CNT_LEN) {
-		struct http_hdr_ctx ctx;
-
 		ctx.blk = NULL;
 		while (http_find_header(htx, ist("Content-Length"), &ctx, 1))
 			http_remove_header(htx, &ctx);
@@ -541,6 +555,20 @@ htx_set_comp_reshdr(struct comp_state *st, struct stream *s, struct http_msg *ms
 			goto error;
 	}
 
+	/* convert "ETag" header to a weak ETag */
+	ctx.blk = NULL;
+	if (http_find_header(htx, ist("ETag"), &ctx, 1)) {
+		if (ctx.value.ptr[0] == '"') {
+			/* This a strong ETag. Convert it to a weak one. */
+			struct ist v = ist2(trash.area, 0);
+			if (istcat(&v, ist("W/"), trash.size) == -1 || istcat(&v, ctx.value, trash.size) == -1)
+				goto error;
+
+			if (!http_replace_header_value(htx, &ctx, v))
+				goto error;
+		}
+	}
+
 	return 1;
 
   error:
@@ -843,6 +871,21 @@ http_select_comp_reshdr(struct comp_state *st, struct stream *s, struct http_msg
 			goto fail;
 	}
 
+	/* no compression when ETag is malformed */
+	ctx.idx = 0;
+	if (http_find_full_header2("ETag", 4, ci_head(c), &txn->hdr_idx, &ctx)) {
+		if (!(((ctx.vlen >= 4 && memcmp(ctx.line + ctx.val, "W/\"", 3) == 0) || /* Either a weak ETag */
+		       (ctx.vlen >= 2 && ctx.line[ctx.val] == '"')) &&                  /* or strong ETag */
+		      ctx.line[ctx.val + ctx.vlen - 1] == '"')) {
+			goto fail;
+		}
+	}
+	/* no compression when multiple ETags are present
+	 * Note: Do not reset ctx.idx!
+	 */
+	if (http_find_full_header2("ETag", 4, ci_head(c), &txn->hdr_idx, &ctx))
+		goto fail;
+
 	comp_type = NULL;
 
 	/* we don't want to compress multipart content-types, nor content-types that are
@@ -939,6 +982,21 @@ htx_select_comp_reshdr(struct comp_state *st, struct stream *s, struct http_msg
 			goto fail;
 	}
 
+	/* no compression when ETag is malformed */
+	ctx.blk = NULL;
+	if (http_find_header(htx, ist("ETag"), &ctx, 1)) {
+		if (!(((ctx.value.len >= 4 && memcmp(ctx.value.ptr, "W/\"", 3) == 0) || /* Either a weak ETag */
+		       (ctx.value.len >= 2 && ctx.value.ptr[0] == '"')) &&              /* or strong ETag */
+		      ctx.value.ptr[ctx.value.len - 1] == '"')) {
+			goto fail;
+		}
+	}
+	/* no compression when multiple ETags are present
+	 * Note: Do not reset ctx.blk!
+	 */
+	if (http_find_header(htx, ist("ETag"), &ctx, 1))
+		goto fail;
+
 	comp_type = NULL;
 
 	/* we don't want to compress multipart content-types, nor content-types that are