diff --git a/include/os/linux/spl/sys/isa_defs.h b/include/os/linux/spl/sys/isa_defs.h
index a032aae91..ee3b74607 100644
--- a/include/os/linux/spl/sys/isa_defs.h
+++ b/include/os/linux/spl/sys/isa_defs.h
@@ -206,9 +206,13 @@
  * RISC-V arch specific defines
  * only RV64G (including atomic) LP64 is supported yet
  */
-#elif defined(__riscv) && defined(_LP64) && _LP64 && \
+#elif defined(__riscv) && defined(__riscv_xlen) && __riscv_xlen == 64 && \
 	defined(__riscv_atomic) && __riscv_atomic
 
+#if !defined(_LP64)
+#define	_LP64 1
+#endif
+
 #ifndef	__riscv__
 #define	__riscv__
 #endif
diff --git a/lib/libspl/include/sys/isa_defs.h b/lib/libspl/include/sys/isa_defs.h
index 756adff15..114cca4f1 100644
--- a/lib/libspl/include/sys/isa_defs.h
+++ b/lib/libspl/include/sys/isa_defs.h
@@ -227,9 +227,13 @@ extern "C" {
  * RISC-V arch specific defines
  * only RV64G (including atomic) LP64 is supported yet
  */
-#elif defined(__riscv) && defined(_LP64) && _LP64 && \
+#elif defined(__riscv) && defined(__riscv_xlen) && __riscv_xlen == 64 && \
 	defined(__riscv_atomic) && __riscv_atomic
 
+#if !defined(_LP64)
+#define	_LP64 1
+#endif
+
 #ifndef	__riscv__
 #define	__riscv__
 #endif