diff --git a/tcl/package_ip.tcl b/tcl/package_ip.tcl
index e113f41..51c16fb 100644
--- a/tcl/package_ip.tcl
+++ b/tcl/package_ip.tcl
@@ -16,7 +16,10 @@ proc DictValueOr { dict key default } {
 # EX: [SplitSub buz.bar foo] => ""
 proc SplitSub { str startword } {
 	if { [string first $startword $str] == 0 } {
-		set sepidx [string first "." "$str"]
+		# Start searching for the delimiter after the start word, otherwise
+		# start words containing a delimiter will yield incorrect results
+		set start_substr_idx [string length $startword]
+		set sepidx [string first "." "$str" $start_substr_idx]
 
 		if { $sepidx == -1 } {
 			return ""