diff --git a/man2/arch_prctl.2 b/man2/arch_prctl.2
index 19caa8788..50a7db98f 100644
--- a/man2/arch_prctl.2
+++ b/man2/arch_prctl.2
@@ -117,7 +117,7 @@ is only needed when you want to set bases that are larger than 4GB.
 Memory in the first 2GB of address space can be allocated by using
 .BR mmap (2)
 with the
-.I MAP_32BIT
+.B MAP_32BIT
 flag.
 
 As of version 2.3.5, glibc provides no prototype for