diff --git a/cvs-1.11.21-diff.patch b/cvs-1.11.21-diff.patch
new file mode 100644
index 0000000..f2a306b
--- /dev/null
+++ b/cvs-1.11.21-diff.patch
@@ -0,0 +1,21 @@
+--- cvs-1.11.21/src/diff.c.old	2005-05-27 19:17:03.000000000 +0200
++++ cvs-1.11.21/src/diff.c	2005-12-15 15:22:05.000000000 +0100
+@@ -955,14 +955,16 @@
+ 	    /* The first revision does not exist.  If EMPTY_FILES is
+                true, treat this as an added file.  Otherwise, warn
+                about the missing tag.  */
+-	    if( use_rev2 == NULL || RCS_isdead( vers->srcfile, use_rev2 ) )
++	    if( use_rev2 == NULL || RCS_isdead( vers->srcfile, use_rev2 ) ) {
+ 		/* At least in the case where DIFF_REV1 and DIFF_REV2
+ 		 * are both numeric (and non-existant (NULL), as opposed to
+ 		 * dead?), we should be returning some kind of error (see
+ 		 * basicb-8a0 in testsuite).  The symbolic case may be more
+ 		 * complicated.
+ 		 */
+-		return DIFF_SAME;
++		error (0, 0, "no revision in file %s or missing file %s", finfo->fullname, finfo->fullname);
++		return DIFF_ERROR;
++	    }
+ 	    if( empty_files )
+ 		return DIFF_ADDED;
+ 	    if( use_rev1 != NULL )
diff --git a/cvs.spec b/cvs.spec
index 16382ed..6c8adc8 100644
--- a/cvs.spec
+++ b/cvs.spec
@@ -24,6 +24,7 @@ Patch8: cvs-1.11.19-tagname.patch
 Patch9: cvs-1.11.19-comp.patch
 Patch11: cvs-1.11.19-tmp.patch
 Patch12: cvs-1.11.21-pam.patch
+Patch13: cvs-1.11.21-diff.patch
 Prereq: /sbin/install-info
 Requires: vim-minimal
 Prefix: %{_prefix}
@@ -67,6 +68,8 @@ release.
 %patch12 -p1 -b .pam
 %endif
 
+%patch13 -p1 -b .diff
+
 # Apply a patch to the generated files, OR
 # run autoreconf and require autoconf >= 2.58, automake >= 1.7.9
 #%patch5 -p1 -b .extzlib2
@@ -135,6 +138,7 @@ fi
 
 %changelog
 * Wed Dec 14 2005 Martin Stransky <stransky@redhat.com> 1.11.21-2
+- fix for cvs diff with two -r switches (#18161)
 - pam patch (#48937)
 - CVS_RSH is set to ssh (#58699)