diff -Nru qtbase-opensource-src-5.11.1+dfsg/debian/changelog qtbase-opensource-src-5.11.1+dfsg/debian/changelog
--- qtbase-opensource-src-5.11.1+dfsg/debian/changelog	2018-08-25 17:59:22.000000000 +0000
+++ qtbase-opensource-src-5.11.1+dfsg/debian/changelog	2018-11-02 11:41:35.000000000 +0000
@@ -1,3 +1,9 @@
+qtbase-opensource-src (5.11.1+dfsg-7ubuntu2) cosmic; urgency=medium
+
+  * Add a patch to pass default include directories to qdoc (LP: #1799111).
+
+ -- Dmitry Shachnev <mitya57@ubuntu.com>  Fri, 02 Nov 2018 14:41:35 +0300
+
 qtbase-opensource-src (5.11.1+dfsg-7ubuntu1) cosmic; urgency=medium
 
   * Merge from Debian Experimental. Remaining changes:
diff -Nru qtbase-opensource-src-5.11.1+dfsg/debian/patches/qdoc_default_incdirs.diff qtbase-opensource-src-5.11.1+dfsg/debian/patches/qdoc_default_incdirs.diff
--- qtbase-opensource-src-5.11.1+dfsg/debian/patches/qdoc_default_incdirs.diff	1970-01-01 00:00:00.000000000 +0000
+++ qtbase-opensource-src-5.11.1+dfsg/debian/patches/qdoc_default_incdirs.diff	2018-11-02 11:41:35.000000000 +0000
@@ -0,0 +1,19 @@
+Description: pass default include directories to qdoc
+Author: Martin Smith <martin.smith@qt.io>
+Bug: https://bugs.debian.org/908328
+Forwarded: no
+Last-Update: 2018-10-29
+
+--- a/mkspecs/features/qt_docs.prf
++++ b/mkspecs/features/qt_docs.prf
+@@ -78,6 +78,10 @@ doc_command = $$QDOC $$QMAKE_DOCS
+ prepare_docs {
+     prepare_docs.commands += $$doc_command -prepare $$PREP_DOC_INDEXES -no-link-errors $(INCPATH)
+     generate_docs.commands += $$doc_command -generate $$DOC_INDEXES $(INCPATH)
++    for (incdir, QMAKE_DEFAULT_INCDIRS) {
++        prepare_docs.commands += -I$$shell_quote($$incdir)
++        generate_docs.commands += -I$$shell_quote($$incdir)
++    }
+     prepare_docs.depends += qtattributionsscanner
+ } else {
+     html_docs.commands += $$doc_command $$DOC_INDEXES $(INCPATH)
diff -Nru qtbase-opensource-src-5.11.1+dfsg/debian/patches/series qtbase-opensource-src-5.11.1+dfsg/debian/patches/series
--- qtbase-opensource-src-5.11.1+dfsg/debian/patches/series	2018-08-25 17:58:09.000000000 +0000
+++ qtbase-opensource-src-5.11.1+dfsg/debian/patches/series	2018-11-02 11:41:35.000000000 +0000
@@ -14,3 +14,4 @@
 armv4.diff
 nonlinux_utime.diff
 no_arc4random_buf.diff
+qdoc_default_incdirs.diff