diff --git a/iocBoot/iocWithAsyn/st.cmd b/iocBoot/iocWithAsyn/st.cmd
index 26181bbb..c00f0d44 100644
--- a/iocBoot/iocWithAsyn/st.cmd
+++ b/iocBoot/iocWithAsyn/st.cmd
@@ -20,6 +20,11 @@
 #< ../nfsCommands
 
 cd appbin
+
+# If the VxWorks kernel was built using the project facility, the following must
+# be added before any C++ code is loaded (see SPR #28980).
+sysCplusEnable=1
+
 ld < WithMPFLib
 
 cd startup
diff --git a/iocBoot/iocWithMPF/st.cmd b/iocBoot/iocWithMPF/st.cmd
index 26181bbb..c00f0d44 100644
--- a/iocBoot/iocWithMPF/st.cmd
+++ b/iocBoot/iocWithMPF/st.cmd
@@ -20,6 +20,11 @@
 #< ../nfsCommands
 
 cd appbin
+
+# If the VxWorks kernel was built using the project facility, the following must
+# be added before any C++ code is loaded (see SPR #28980).
+sysCplusEnable=1
+
 ld < WithMPFLib
 
 cd startup