diff --git a/ci/test/00_setup_env_i686_multiprocess.sh b/ci/test/00_setup_env_i686_multiprocess.sh
index 00a4d781c2fda..f6463438d3959 100755
--- a/ci/test/00_setup_env_i686_multiprocess.sh
+++ b/ci/test/00_setup_env_i686_multiprocess.sh
@@ -14,5 +14,5 @@ export DEP_OPTS="DEBUG=1 MULTIPROCESS=1"
 export GOAL="install"
 export TEST_RUNNER_EXTRA="--v2transport"
 export BITCOIN_CONFIG="--enable-debug CC='clang -m32' CXX='clang++ -m32' \
-CPPFLAGS='-DBOOST_MULTI_INDEX_ENABLE_SAFE_MODE'"
+CPPFLAGS='-DBOOST_MULTI_INDEX_ENABLE_SAFE_MODE' CXXFLAGS='-Wno-error=documentation'"
 export BITCOIND=bitcoin-node  # Used in functional tests
diff --git a/ci/test/00_setup_env_win64.sh b/ci/test/00_setup_env_win64.sh
index bce5ee74b6191..bf80d5d435f0e 100755
--- a/ci/test/00_setup_env_win64.sh
+++ b/ci/test/00_setup_env_win64.sh
@@ -16,4 +16,4 @@ export GOAL="deploy"
 # Prior to 11.0.0, the mingw-w64 headers were missing noreturn attributes, causing warnings when
 # cross-compiling for Windows. https://sourceforge.net/p/mingw-w64/bugs/306/
 # https://github.com/mingw-w64/mingw-w64/commit/1690994f515910a31b9fb7c7bd3a52d4ba987abe
-export BITCOIN_CONFIG="--enable-reduce-exports --disable-gui-tests CXXFLAGS=-Wno-return-type"
+export BITCOIN_CONFIG="--enable-reduce-exports --disable-gui-tests CXXFLAGS='-Wno-return-type -Wno-error=maybe-uninitialized -Wno-error=array-bounds'"
diff --git a/configure.ac b/configure.ac
index c7d124a1f174d..ee4400f21aa70 100644
--- a/configure.ac
+++ b/configure.ac
@@ -401,37 +401,35 @@ if test "$enable_werror" = "yes"; then
   ERROR_CXXFLAGS=$CXXFLAG_WERROR
 fi
 
-if test "$CXXFLAGS_overridden" = "no"; then
-  AX_CHECK_COMPILE_FLAG([-Wall], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wall"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wextra], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wextra"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wgnu], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wgnu"], [], [$CXXFLAG_WERROR])
-  dnl some compilers will ignore -Wformat-security without -Wformat, so just combine the two here.
-  AX_CHECK_COMPILE_FLAG([-Wformat -Wformat-security], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wformat -Wformat-security"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wvla], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wvla"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wshadow-field], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wshadow-field"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wthread-safety], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wthread-safety"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wloop-analysis], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wloop-analysis"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wredundant-decls], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wredundant-decls"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wunused-member-function], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wunused-member-function"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wdate-time], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wdate-time"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wconditional-uninitialized], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wconditional-uninitialized"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wduplicated-branches], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wduplicated-branches"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wduplicated-cond], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wduplicated-cond"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wlogical-op], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wlogical-op"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Woverloaded-virtual], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Woverloaded-virtual"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wsuggest-override], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wsuggest-override"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wimplicit-fallthrough"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wunreachable-code], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wunreachable-code"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wdocumentation], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wdocumentation"], [], [$CXXFLAG_WERROR])
-
-  dnl Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
-  dnl unknown options if any other warning is produced. Test the -Wfoo case, and
-  dnl set the -Wno-foo case if it works.
-  AX_CHECK_COMPILE_FLAG([-Wunused-parameter], [NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-unused-parameter"], [], [$CXXFLAG_WERROR])
-  AX_CHECK_COMPILE_FLAG([-Wself-assign], [NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-self-assign"], [], [$CXXFLAG_WERROR])
-  if test "$suppress_external_warnings" != "yes" ; then
-    AX_CHECK_COMPILE_FLAG([-Wdeprecated-copy], [NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-deprecated-copy"], [], [$CXXFLAG_WERROR])
-  fi
+AX_CHECK_COMPILE_FLAG([-Wall], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wall"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wextra], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wextra"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wgnu], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wgnu"], [], [$CXXFLAG_WERROR])
+dnl some compilers will ignore -Wformat-security without -Wformat, so just combine the two here.
+AX_CHECK_COMPILE_FLAG([-Wformat -Wformat-security], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wformat -Wformat-security"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wvla], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wvla"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wshadow-field], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wshadow-field"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wthread-safety], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wthread-safety"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wloop-analysis], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wloop-analysis"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wredundant-decls], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wredundant-decls"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wunused-member-function], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wunused-member-function"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wdate-time], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wdate-time"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wconditional-uninitialized], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wconditional-uninitialized"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wduplicated-branches], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wduplicated-branches"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wduplicated-cond], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wduplicated-cond"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wlogical-op], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wlogical-op"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Woverloaded-virtual], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Woverloaded-virtual"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wsuggest-override], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wsuggest-override"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wimplicit-fallthrough"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wunreachable-code], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wunreachable-code"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wdocumentation], [WARN_CXXFLAGS="$WARN_CXXFLAGS -Wdocumentation"], [], [$CXXFLAG_WERROR])
+
+dnl Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
+dnl unknown options if any other warning is produced. Test the -Wfoo case, and
+dnl set the -Wno-foo case if it works.
+AX_CHECK_COMPILE_FLAG([-Wunused-parameter], [NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-unused-parameter"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-Wself-assign], [NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-self-assign"], [], [$CXXFLAG_WERROR])
+if test "$suppress_external_warnings" != "yes" ; then
+  AX_CHECK_COMPILE_FLAG([-Wdeprecated-copy], [NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-deprecated-copy"], [], [$CXXFLAG_WERROR])
 fi
 
 dnl Don't allow extended (non-ASCII) symbols in identifiers. This is easier for code review.