diff --git a/mkspecs/common/linux.conf b/mkspecs/common/linux.conf
index 1a39c88425b..13916a5646f 100644
--- a/mkspecs/common/linux.conf
+++ b/mkspecs/common/linux.conf
@@ -36,7 +36,6 @@ QMAKE_LIBS_OPENGL_ES2   = -lGLESv2
 QMAKE_LIBS_OPENVG       = -lOpenVG
 QMAKE_LIBS_THREAD       = -lpthread
 
-QMAKE_CFLAGS_WAYLAND    =
 QMAKE_INCDIR_WAYLAND    =
 QMAKE_LIBS_WAYLAND_CLIENT = -lwayland-client
 QMAKE_LIBS_WAYLAND_SERVER = -lwayland-server
diff --git a/mkspecs/features/qmake_use.prf b/mkspecs/features/qmake_use.prf
index a8e2e6c4171..81b841d4571 100644
--- a/mkspecs/features/qmake_use.prf
+++ b/mkspecs/features/qmake_use.prf
@@ -10,16 +10,17 @@ for(ever) {
         else: \
             libs = $$eval(QMAKE_LIBS_$${nu}_RELEASE)
         libs += $$eval(QMAKE_LIBS_$$nu)
-        cflags = $$eval(QMAKE_CFLAGS_$${nu})
+        defines = $$eval(QMAKE_DEFINES_$${nu})
+        includes = $$eval(QMAKE_INCDIR_$${nu})
 
-        isEmpty(libs):isEmpty(cflags): \
+        isEmpty(libs):isEmpty(defines):isEmpty(includes): \
             error("Library '$$name' is not defined.")
 
         !contains(use, nolink): \
             LIBS$${suffix} += $$libs
         !contains(use, linkonly) {
-            QMAKE_CFLAGS += $$cflags
-            QMAKE_CXXFLAGS += $$cflags
+            DEFINES += $$defines
+            INCLUDEPATH += $$includes
         }
     }
     !isEmpty(suffix): break()
diff --git a/mkspecs/features/qt_configure.prf b/mkspecs/features/qt_configure.prf
index 58e0b1c88ea..7f575b8a1be 100644
--- a/mkspecs/features/qt_configure.prf
+++ b/mkspecs/features/qt_configure.prf
@@ -475,8 +475,6 @@ defineTest(qtConfLibrary_inline) {
     !isEmpty(prefix) {
         $${1}.includedir = $$prefix/include
         export($${1}.includedir)
-        $${1}.cflags = -I$$prefix/include
-        export($${1}.cflags)
         $${1}.libs = "-L$$prefix/lib $$eval($${1}.libs)"
         export($${1}.libs)
     }
@@ -493,8 +491,6 @@ defineTest(qtConfLibrary_makeSpec) {
 
     $${1}.includedir = "$$val_escape(QMAKE_INCDIR_$$spec)"
     export($${1}.includedir)
-    $${1}.cflags = "$$val_escape(QMAKE_CFLAGS_$$spec)"
-    export($${1}.cflags)
     libs =
     for (l, QMAKE_LIBDIR_$$spec): \
         libs += -L$$l
@@ -522,15 +518,8 @@ defineTest(qtConfLibrary_pkgConfig) {
     qtRunLoggedCommand("$$pkg_config --modversion $$args", version)|return(false)
     qtRunLoggedCommand("$$pkg_config --libs-only-L --libs-only-l $$args", $${1}.libs)|return(false)
     qtRunLoggedCommand("$$pkg_config --cflags $$args", $${1}.cflags)|return(false)
-    qtRunLoggedCommand("$$pkg_config --cflags-only-I $$args", includes)|return(false)
-    eval(includes = $$includes)
-    includes ~= s/^-I//g
-    $${1}.includedir = "$$val_escape(includes)"
     version ~= s/[^0-9.].*$//
     $${1}.version = $$first(version)
-    export($${1}.libs)
-    export($${1}.cflags)
-    export($${1}.includedir)
     export($${1}.version)
     return(true)
 }
@@ -562,6 +551,9 @@ defineReplace(qtConfLibraryArgs) {
     includedir = $$eval($${1}.includedir)
     !isEmpty(includedir): \
         qmake_args += $$system_quote(INCLUDEPATH *= $$includedir)
+    cflags = $$eval($${1}.cflags)
+    !isEmpty(cflags): \
+        qmake_args += $$system_quote(QMAKE_CFLAGS += $$cflags) $$system_quote(QMAKE_CXXFLAGS += $$cflags)
     return($$qmake_args)
 }
 
@@ -588,12 +580,31 @@ defineTest(qtConfExportLibrary) {
     eval(includes = $$eval($${1}.includedir))
     version = $$eval($${1}.version)
 
+    # Split $$cflags into stuff that goes into DEFINES, INCLUDEPATH, and other stuff.
+    defines =
+    ignored =
+    for (i, cflags) {
+        contains(i, "-I.*") {
+            i ~= s/^-I//
+            includes += $$i
+        } else: contains(i, "-D.*") {
+            i ~= s/^-D//
+            defines += $$i
+        } else {
+            # Sometimes, pkg-config files or *-config scripts include other flags
+            # we really don't need and shouldn't add (pg_config is really bad).
+            ignored += $$i
+        }
+    }
+    !isEmpty(ignored): \
+        qtConfAddNote("Dropped compiler flags '$$ignored' when detecting library '$$2'.")
+
     NAME = $$upper($$2)
     !isEmpty(libs): qtConfOutputVar(assign, $$output, QMAKE_LIBS_$$NAME, $$libs)
     for (b, $${1}.builds._KEYS_): \
         qtConfOutputVar(assign, $$output, QMAKE_LIBS_$${NAME}_$$upper($$b), \
                                           $$eval($${1}.builds.$${b}))
-    !isEmpty(cflags): qtConfOutputVar(assign, $$output, QMAKE_CFLAGS_$$NAME, $$cflags)
+    !isEmpty(defines): qtConfOutputVar(assign, $$output, QMAKE_DEFINES_$$NAME, $$defines)
     !isEmpty(includes): qtConfOutputVar(assign, $$output, QMAKE_INCDIR_$$NAME, $$includes)
     !isEmpty(version) {
         qtConfOutputVar(assign, $$output, QMAKE_$${NAME}_VERSION, $$version)
diff --git a/src/sql/configure.pri b/src/sql/configure.pri
index 948808f4f77..1d8847b4bc1 100644
--- a/src/sql/configure.pri
+++ b/src/sql/configure.pri
@@ -22,11 +22,8 @@ defineTest(qtConfLibrary_psqlConfig) {
         $${1}.libs = "$$val_escape(libs)"
         includedir -= $$QMAKE_DEFAULT_INCDIRS
         $${1}.includedir = "$$val_escape(includedir)"
-        !isEmpty(includedir): \
-            $${1}.cflags = "-I$$val_escape(includedir)"
         export($${1}.libs)
         export($${1}.includedir)
-        export($${1}.cflags)
         return(true)
     }
     return(false)
@@ -65,11 +62,8 @@ defineTest(qtConfLibrary_mysqlConfig) {
         includedir ~= s/^-I//g
         includedir -= $$QMAKE_DEFAULT_INCDIRS
         $${1}.includedir = "$$val_escape(includedir)"
-        !isEmpty(includedir): \
-            $${1}.cflags = "-I$$val_escape(includedir)"
         export($${1}.libs)
         export($${1}.includedir)
-        export($${1}.cflags)
         return(true)
     }
     return(false)