diff --git a/cipher/asm-common-aarch64.h b/cipher/asm-common-aarch64.h
index dde7366c..bbc8ee1e 100644
--- a/cipher/asm-common-aarch64.h
+++ b/cipher/asm-common-aarch64.h
@@ -61,6 +61,12 @@
 # define AARCH64_PAC_PROPERTY_FLAG 0 /* No PAC */
 #endif
 
+#if defined(__ARM_FEATURE_GCS_DEFAULT) && __ARM_FEATURE_GCS_DEFAULT == 1
+# define AARCH64_GCS_PROPERTY_FLAG (1 << 2)
+#else
+# define AARCH64_GCS_PROPERTY_FLAG 0 /* No GCS */
+#endif
+
 #ifdef HAVE_GCC_ASM_CFI_DIRECTIVES
 /* CFI directives to emit DWARF stack unwinding information. */
 # define CFI_STARTPROC()            .cfi_startproc; AARCH64_HINT_BTI_C
@@ -154,10 +160,13 @@
 	ldp d8, d9, [sp], #16; \
 	CFI_ADJUST_CFA_OFFSET(-16);
 
-#if (AARCH64_BTI_PROPERTY_FLAG | AARCH64_PAC_PROPERTY_FLAG)
-/* Generate PAC/BTI property for all assembly files including this header.
+#if (AARCH64_BTI_PROPERTY_FLAG | AARCH64_PAC_PROPERTY_FLAG | AARCH64_GCS_PROPERTY_FLAG)
+/* Generate GCS/PAC/BTI property for all assembly files including this header.
  *
  * libgcrypt support these extensions:
+ *  - Armv9.4-A Guarded Control Stack (GCS):
+ *    We mark GCS as supported.  FIXME: Returns must match the expected value.
+ *
  *  - Armv8.3-A Pointer Authentication (PAC):
  *    As currently all AArch64 assembly functions are leaf functions and do
  *    not store/load link register LR, we just mark PAC as supported.
@@ -178,7 +187,7 @@ ELF(.balign 8)
 ELF(.long 0xc0000000)
 ELF(.long 3f - 2f)
 ELF(2:)
-ELF(.long (AARCH64_BTI_PROPERTY_FLAG | AARCH64_PAC_PROPERTY_FLAG))
+ELF(.long (AARCH64_BTI_PROPERTY_FLAG | AARCH64_PAC_PROPERTY_FLAG | AARCH64_GCS_PROPERTY_FLAG))
 ELF(3:)
 ELF(.balign 8)
 ELF(4:)