diff --git a/config/always-compiler-options.m4 b/config/always-compiler-options.m4
index e187f6ff8..f903655fa 100644
--- a/config/always-compiler-options.m4
+++ b/config/always-compiler-options.m4
@@ -22,7 +22,7 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_CC_ASAN], [
 	AS_IF([ test "$enable_asan" = "yes" ], [
 		AC_MSG_CHECKING([whether $CC supports -fsanitize=address])
 		saved_cflags="$CFLAGS"
-		CFLAGS="$CFLAGS -fsanitize=address"
+		CFLAGS="$CFLAGS -Werror -fsanitize=address"
 		AC_LINK_IFELSE([
 			AC_LANG_SOURCE([[ int main() { return 0; } ]])
 		], [
@@ -52,7 +52,7 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_CC_FRAME_LARGER_THAN], [
 	AC_MSG_CHECKING([whether $CC supports -Wframe-larger-than=<size>])
 
 	saved_flags="$CFLAGS"
-	CFLAGS="$CFLAGS -Wframe-larger-than=4096"
+	CFLAGS="$CFLAGS -Werror -Wframe-larger-than=4096"
 
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])], [
 		FRAME_LARGER_THAN="-Wframe-larger-than=4096"
@@ -73,7 +73,7 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_CC_NO_FORMAT_TRUNCATION], [
 	AC_MSG_CHECKING([whether $CC supports -Wno-format-truncation])
 
 	saved_flags="$CFLAGS"
-	CFLAGS="$CFLAGS -Wno-format-truncation"
+	CFLAGS="$CFLAGS -Werror -Wno-format-truncation"
 
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])], [
 		NO_FORMAT_TRUNCATION=-Wno-format-truncation
@@ -100,7 +100,7 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_CC_NO_BOOL_COMPARE], [
 	AC_MSG_CHECKING([whether $CC supports -Wno-bool-compare])
 
 	saved_flags="$CFLAGS"
-	CFLAGS="$CFLAGS -Wbool-compare"
+	CFLAGS="$CFLAGS -Werror -Wbool-compare"
 
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])], [
 		NO_BOOL_COMPARE=-Wno-bool-compare
@@ -126,7 +126,7 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_CC_NO_UNUSED_BUT_SET_VARIABLE], [
 	AC_MSG_CHECKING([whether $CC supports -Wno-unused-but-set-variable])
 
 	saved_flags="$CFLAGS"
-	CFLAGS="$CFLAGS -Wunused-but-set-variable"
+	CFLAGS="$CFLAGS -Werror -Wunused-but-set-variable"
 
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])], [
 		NO_UNUSED_BUT_SET_VARIABLE=-Wno-unused-but-set-variable
@@ -147,7 +147,7 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_CC_NO_OMIT_FRAME_POINTER], [
 	AC_MSG_CHECKING([whether $CC supports -fno-omit-frame-pointer])
 
 	saved_flags="$CFLAGS"
-	CFLAGS="$CFLAGS -fno-omit-frame-pointer"
+	CFLAGS="$CFLAGS -Werror -fno-omit-frame-pointer"
 
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])], [
 		NO_OMIT_FRAME_POINTER=-fno-omit-frame-pointer