diff --git a/PROMS/Volian.Controls.Library/vlnTreeView.cs b/PROMS/Volian.Controls.Library/vlnTreeView.cs
index 99d94191..2224c20b 100644
--- a/PROMS/Volian.Controls.Library/vlnTreeView.cs
+++ b/PROMS/Volian.Controls.Library/vlnTreeView.cs
@@ -1514,7 +1514,7 @@ namespace Volian.Controls.Library
 							//				can do Before/After - no links exist in pasted step, treat like an insert..
 							//				cannot do Replace
 							//		3) 'to' step is 'source' and 'from' step is same docversion 'source'
-							//				can do Before/After/Replace
+							//				can do Before/After/Replace  (Note that replace is not allowed per B2017-183)
 							StepConfig stpToCfg = iiPasteHere.MyConfig as StepConfig;
 							StepConfig stpFromCfg = iiClipboard.MyConfig as StepConfig;
 
@@ -1529,7 +1529,11 @@ namespace Volian.Controls.Library
 								stpCanPaste = true;
 								okToReplace = false;
 							}
-							else if (stpToIsSource && iiPasteHere.MyDocVersion.VersionID == iiClipboard.MyDocVersion.VersionID) stpCanPaste = true;		// 3)
+							else if (stpToIsSource && iiPasteHere.MyDocVersion.VersionID == iiClipboard.MyDocVersion.VersionID) // 3
+							{
+								stpCanPaste = true;
+								if (stpFromIsSource) okToReplace = false;		// B2017-183: don't allow a replace to source steps
+							}
 							if (iiClipboard.IsRtfRaw) stpCanPaste = false;   // never paste an equation.
 							if (stpCanPaste && AddToInsertMenu(iiPasteHere, 0)) cm.MenuItems.Add("Paste Step Before", new EventHandler(mi_Click));
 							if (stpCanPaste && okToReplace) cm.MenuItems.Add("Replace Existing Step", new EventHandler(mi_Click));