diff --git a/pkgs/development/libraries/qt-5/5.12/default.nix b/pkgs/development/libraries/qt-5/5.12/default.nix
index afca6c7969b4..bdefca45a9af 100644
--- a/pkgs/development/libraries/qt-5/5.12/default.nix
+++ b/pkgs/development/libraries/qt-5/5.12/default.nix
@@ -67,6 +67,11 @@ let
         ./qtbase.patch.d/0010-qtbase-qtpluginpath.patch
         ./qtbase.patch.d/0011-qtbase-assert.patch
         ./qtbase.patch.d/0012-fix-header_module.patch
+
+        # Ensure -I${includedir} is added to Cflags in pkg-config files.
+        # See https://github.com/NixOS/nixpkgs/issues/52457
+        ./qtbase.patch.d/0014-qtbase-pkg-config.patch
+
         # https://bugreports.qt.io/browse/QTBUG-81715
         # remove after updating to qt > 5.12.7
         (fetchpatch {
diff --git a/pkgs/development/libraries/qt-5/5.12/qtbase.patch.d/0014-qtbase-pkg-config.patch b/pkgs/development/libraries/qt-5/5.12/qtbase.patch.d/0014-qtbase-pkg-config.patch
new file mode 100644
index 000000000000..90caaea1cf4d
--- /dev/null
+++ b/pkgs/development/libraries/qt-5/5.12/qtbase.patch.d/0014-qtbase-pkg-config.patch
@@ -0,0 +1,14 @@
+diff --git a/qmake/generators/makefile.cpp b/qmake/generators/makefile.cpp
+--- a/qmake/generators/makefile.cpp
++++ b/qmake/generators/makefile.cpp
+@@ -3390,8 +3390,7 @@ MakefileGenerator::writePkgConfigFile()
+       << varGlue("QMAKE_PKGCONFIG_CFLAGS", "", " ", " ")
+         //      << varGlue("DEFINES","-D"," -D"," ")
+          ;
+-    if (!project->values("QMAKE_DEFAULT_INCDIRS").contains(includeDir))
+-        t << "-I${includedir}";
++    t << "-I${includedir}";
+     if (target_mode == TARG_MAC_MODE && project->isActiveConfig("lib_bundle")
+         && libDir != QLatin1String("/Library/Frameworks")) {
+             t << " -F${libdir}";
+