diff --git a/srcpkgs/mongoose/template b/srcpkgs/mongoose/template
index c9e41c4f7a2e24..569a4cf5c96153 100644
--- a/srcpkgs/mongoose/template
+++ b/srcpkgs/mongoose/template
@@ -14,24 +14,49 @@ license="GPL-2.0-only"
 homepage="https://mongoose.ws/"
 distfiles="https://github.com/cesanta/mongoose/archive/${version}.tar.gz"
 checksum=1ef09d971b6de1a6317c109980d6fb5a9c19b39efef2506d6b76869644b3dafa
-
+CFLAGS="-fPIC -Wno-error=unused-function" # fix-tests.patch causes unused-function
 export SSL=OPENSSL
-CFLAGS+=" -fPIC"
 
-case "$XBPS_TARGET_MACHINE" in
-	*-musl) CFLAGS+=" -Wno-error=sign-conversion"	# FD(c_) macro is broken
-		make_check_args+=" NO_SANITIZE=1" ;;	# libsanitizer-devel unavailable
-	*)	checkdepends+=" libsanitizer-devel" ;;
-esac
+if [ "$XBPS_TARGET_LIBC" = musl ]; then
+	# libsanitizer-devel is currenly not available on musl
+	make_check_args+=" NO_SANITIZE=1"
+else
+	checkdepends+=" libsanitizer-devel"
+fi
 
 # GitHub CI runner doesn't support IPv6, causing tests to fail
 if [ "$XBPS_BUILD_ENVIRONMENT" = "void-packages-ci" ]; then
 	make_check_args+=" IPV6=0"
 fi
 
-pre_check() {
-	# -Wunused-function -Werror and fix-tests.patch are enemies
-	CFLAGS+=" -Wno-error=unused-function"
+post_extract() {
+	if [ "$XBPS_TARGET_LIBC" = musl ]; then
+		# GCC falsely flags musl's FD_{SET,ISSET,CLR} macros as -Wsign-conversion
+		#	https://github.com/cesanta/mongoose/issues/1501#issuecomment-1082750154
+		#	https://inbox.vuxu.org/musl/20200803174707.GF6949@brightrain.aerifal.cx/T/
+		vsed -i src/sock.c -e '
+/[[:space:]]FD_SET(/b label
+/[[:space:]]FD_ISSET(/b label
+/[[:space:]]FD_CLR(/b label
+b
+:label
+i\
+#pragma GCC diagnostic push\
+#pragma GCC diagnostic ignored "-Wsign-conversion"
+p
+i\
+#pragma GCC diagnostic pop
+d'
+		# What the above sed script does -
+		# Searches for FD_{SET,ISSET,CLR}
+		# - If found, jump to the line after :label
+		# - If not found, go to the end of the script (print current line as-is)
+		# :label
+		# - [i] Insert the two #pragma lines
+		# - [p] Insert the current line
+		# - [i] Insert the remaining #pragma line
+		# - [d] Proceed to the next line of input
+	fi
 }
 
 mongoose-devel_package() {