diff --git a/extensions/openpower-pels/fru_identity.cpp b/extensions/openpower-pels/fru_identity.cpp
index 15a7bda..0b1426d 100644
--- a/extensions/openpower-pels/fru_identity.cpp
+++ b/extensions/openpower-pels/fru_identity.cpp
@@ -213,9 +213,9 @@
     auto pn = partNumber;
 
     // Strip leading whitespace on this one.
-    while (' ' == pn.front())
+    while (!pn.empty() && (' ' == pn.front()))
     {
-        pn = pn.substr(1);
+        pn.erase(0, 1);
     }
 
     fillArray(pn, _pnOrProcedureID);