diff --git a/include/lib/aarch64/arch_helpers.h b/include/lib/aarch64/arch_helpers.h
index 7d24a53..65941e6 100644
--- a/include/lib/aarch64/arch_helpers.h
+++ b/include/lib/aarch64/arch_helpers.h
@@ -270,6 +270,8 @@
 DEFINE_SYSREG_RW_FUNCS(vpidr_el2)
 DEFINE_SYSREG_RW_FUNCS(vmpidr_el2)
 
+DEFINE_SYSREG_READ_FUNC(isr_el1)
+
 /* GICv3 System Registers */
 
 DEFINE_RENAME_SYSREG_RW_FUNCS(icc_sre_el1, ICC_SRE_EL1)