diff --git a/mkspecs/features/qt_docs.prf b/mkspecs/features/qt_docs.prf
index 095bf15d..5178a7d8 100644
--- a/mkspecs/features/qt_docs.prf
+++ b/mkspecs/features/qt_docs.prf
@@ -98,6 +98,10 @@ doc_command = $$QDOC $$QMAKE_DOCS
 prepare_docs {
     prepare_docs.commands += $$doc_command -prepare $$PREP_DOC_INDEXES -no-link-errors $$QDOC_INCLUDE_PATHS
     generate_docs.commands += $$doc_command -generate $$DOC_INDEXES $$QDOC_INCLUDE_PATHS
+    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 $(QDOC_INCLUDE_PATHS)