diff --git a/usr.bin/bsdiff/bsdiff/bsdiff.1 b/usr.bin/bsdiff/bsdiff/bsdiff.1
index 5c608b44c426..4ceb9ed5bb0c 100644
--- a/usr.bin/bsdiff/bsdiff/bsdiff.1
+++ b/usr.bin/bsdiff/bsdiff/bsdiff.1
@@ -65,5 +65,24 @@ an absolute minimum working set size of 8 times the size of
 .Ar oldfile .
 .Sh SEE ALSO
 .Xr bspatch 1
+.Sh BUGS
+The
+.Nm
+utility does not store the hashes of
+.Ar oldfile
+or 
+.Ar newfile
+in
+.Ar patchfile .
+As a result, it is possible to apply a patch to the wrong file; this
+will usually produce garbage.
+It is recommended that users of
+.Nm
+store the hashes of
+.Ar oldfile
+and
+.Ar newfile
+and compare against them before and after applying
+.Ar patchfile .
 .Sh AUTHORS
 .An Colin Percival Aq cperciva@FreeBSD.org
diff --git a/usr.bin/bsdiff/bspatch/bspatch.1 b/usr.bin/bsdiff/bspatch/bspatch.1
index 894bc5075225..29b8db3c81ec 100644
--- a/usr.bin/bsdiff/bspatch/bspatch.1
+++ b/usr.bin/bsdiff/bspatch/bspatch.1
@@ -61,5 +61,26 @@ but can tolerate a very small working set without a dramatic loss
 of performance.
 .Sh SEE ALSO
 .Xr bsdiff 1
+.Sh BUGS
+The
+.Nm
+utility does not verify that
+.Ar oldfile
+is the correct source file for
+.Ar patchfile .
+Attempting to apply a patch to the wrong file will usually produce
+garbage; consequently it is strongly recommended that users of
+.Nm
+verify that
+.Ar oldfile
+matches the source file from which
+.Ar patchfile
+was built, by comparing cryptographic hashes, for example.
+Users may also wish to verify after running
+.Nm
+that
+.Ar newfile
+matches the target file from which
+.Ar was built.
 .Sh AUTHORS
 .An Colin Percival Aq cperciva@FreeBSD.org