diff --git a/.github/workflows/ccpp.yml b/.github/workflows/ccpp.yml
index a3e2ff387..341a1e713 100644
--- a/.github/workflows/ccpp.yml
+++ b/.github/workflows/ccpp.yml
@@ -31,12 +31,12 @@ jobs:
     - uses: msys2/setup-msys2@v2
       with:
         update: true
-        msystem: MINGW32
+        msystem: UCRT64
         install: >-
           make
-          mingw-w64-i686-gcc
-          mingw-w64-i686-lua
-          mingw-w64-i686-nsis
+          mingw-w64-ucrt-x86_64-gcc
+          mingw-w64-ucrt-x86_64-lua
+          mingw-w64-ucrt-x86_64-nsis
           ninja
           bison
           flex
diff --git a/mach/proto/as/comm4.c b/mach/proto/as/comm4.c
index 756f2d4c0..a521fe85f 100644
--- a/mach/proto/as/comm4.c
+++ b/mach/proto/as/comm4.c
@@ -16,6 +16,7 @@
 #include	"comm1.h"
 #include	"y.tab.h"
 #include	"object.h"
+#include <errno.h>
 
 extern YYSTYPE	yylval;
 
@@ -142,10 +143,17 @@ pass_1(int argc, char **argv)
 #endif
 
 	tempfile = tmpfile();
+	if (!tempfile)
+		fatal("couldn't create temporary file: %s", strerror(errno));
+
 #ifdef LISTING
 	listmode = dflag;
 	if (listmode & 0440)
+	{
 		listfile = tmpfile();
+		if (!listfile)
+			fatal("couldn't create temporary file: %s", strerror(errno));
+	}
 #endif
 	for (ip = keytab; ip->i_type; ip++)
 		item_insert(ip, H_KEY+hash(ip->i_name));