diff --git a/Makefile b/Makefile
index ffb085f..33bfb0a 100644
--- a/Makefile
+++ b/Makefile
@@ -146,7 +146,7 @@ _forktest: forktest.o $(ULIB)
 	$(OBJDUMP) -S _forktest > forktest.asm
 
 mkfs: mkfs.c fs.h
-	gcc -m32 -Werror -Wall -o mkfs mkfs.c
+	gcc -Werror -Wall -o mkfs mkfs.c
 
 UPROGS=\
 	_cat\
diff --git a/mkfs.c b/mkfs.c
index f015edd..b50b503 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -11,6 +11,10 @@
 #include "stat.h"
 #include "param.h"
 
+#ifndef _LP64
+#error "Integers are not 32 bits"
+#endif
+
 int nblocks = 985;
 int nlog = LOGSIZE;
 int ninodes = 200;