diff --git a/findversion.sh b/findversion.sh
--- a/findversion.sh
+++ b/findversion.sh
@@ -117,7 +117,11 @@ elif [ -d "$ROOT_DIR/.hg" ]; then
 		BRANCH=""
 		REV="$TAG"
 	fi
-	REV_NR=`LC_ALL=C hg log -f -k "(svn r" -l 1 --template "{desc}\n" | head -n 1 | sed "s@.*(svn r\([0-9]*\)).*@\1@"`
+	REV_NR=`LC_ALL=C hg log -f -k "(svn r" -l 1 --template "{desc|firstline}\n" | grep "^(svn r[0-9]*)" | sed "s@.*(svn r\([0-9]*\)).*@\1@"`
+	if [ -z "$REV_NR" ]; then
+		# No rev? Maybe it is a custom hgsubversion clone
+		REV_NR=`LC_ALL=C hg parent --template="{svnrev}"`
+	fi
 elif [ -f "$ROOT_DIR/.ottdrev" ]; then
 	# We are an exported source bundle
 	cat $ROOT_DIR/.ottdrev
diff --git a/projects/determineversion.vbs b/projects/determineversion.vbs
--- a/projects/determineversion.vbs
+++ b/projects/determineversion.vbs
@@ -278,11 +278,23 @@ Function DetermineSVNVersion()
 							End If ' line <> "default"
 						End If ' Err.Number = 0
 
-						Set oExec = WshShell.Exec("hg log -f -k " & Chr(34) & "(svn r" & Chr(34) & " -l 1 --template " & Chr(34) & "{desc}\n" & Chr(34) & " --cwd ../")
+						Set oExec = WshShell.Exec("hg log -f -k " & Chr(34) & "(svn r" & Chr(34) & " -l 1 --template " & Chr(34) & "{desc|firstline}\n" & Chr(34) & " --cwd ../")
 						If Err.Number = 0 Then
-							revision = Mid(OExec.StdOut.ReadLine(), 7)
-							revision = Mid(revision, 1, InStr(revision, ")") - 1)
+							line = oExec.StdOut.ReadLine()
+							If Left(line, 6) = "(svn r" Then
+								revision = Mid(line, 7)
+								revision = Mid(revision, 1, InStr(revision, ")") - 1)
+							End If 'Left(line, 6) = "(svn r"
 						End If ' Err.Number = 0
+
+						If revision = "" Then
+							' No rev? Maybe it is a custom hgsubversion clone
+							Err.Clear
+							Set oExec = WshShell.Exec("hg parent --template=" & Chr(34) & "{svnrev}" & Chr(34))
+							If Err.Number = 0 Then
+								revision = oExec.StdOut.ReadLine()
+							End If ' Err.Number = 0
+						End If ' revision = ""
 					End If ' Err.Number = 0
 				End If ' oExec.ExitCode = 0
 			End If ' Err.Number = 0