diff --git a/doc/OpenSTA.odt b/doc/OpenSTA.odt
index 4944f292..9ed813c8 100644
Binary files a/doc/OpenSTA.odt and b/doc/OpenSTA.odt differ
diff --git a/doc/OpenSTA.pdf b/doc/OpenSTA.pdf
index eef3c2f8..c5ee6c39 100644
Binary files a/doc/OpenSTA.pdf and b/doc/OpenSTA.pdf differ
diff --git a/tcl/Sdc.tcl b/tcl/Sdc.tcl
index 0bbe9761..6589793e 100644
--- a/tcl/Sdc.tcl
+++ b/tcl/Sdc.tcl
@@ -1668,7 +1668,13 @@ proc set_clock_uncertainty { args } {
   
   if { [info exists keys(-to)] } {
     set to_key "-to"
-    set to_rf "rise_fall"
+    if { [info exists flags(-rise)] } {
+      set to_rf "rise"
+    } elseif { [info exists flags(-fall)] } {
+      set to_rf "fall"
+    } else {
+      set to_rf "rise_fall"
+    }
   } elseif { [info exists keys(-rise_to)] } {
     set to_key "-rise_to"
     set to_rf "rise"