diff --git a/allocator_config.h b/allocator_config.h
index 6430606..d06f6df 100644
--- a/allocator_config.h
+++ b/allocator_config.h
@@ -169,8 +169,14 @@
   static const bool MaySupportMemoryTagging = false;
 
   typedef SizeClassAllocator64<FuchsiaConfig> Primary;
+// Support 39-bit VMA for riscv-64
+#if SCUDO_RISCV64
+  static const uptr PrimaryRegionSizeLog = 28U;
+  static const uptr PrimaryGroupSizeLog = 19U;
+#else
   static const uptr PrimaryRegionSizeLog = 30U;
   static const uptr PrimaryGroupSizeLog = 21U;
+#endif
   typedef u32 PrimaryCompactPtrT;
   static const bool PrimaryEnableRandomOffset = true;
   static const uptr PrimaryMapSizeIncrement = 1UL << 18;
diff --git a/platform.h b/platform.h
index db4217d..aae3b9a 100644
--- a/platform.h
+++ b/platform.h
@@ -37,6 +37,12 @@
 #define SCUDO_TRUSTY 0
 #endif
 
+#if defined(__riscv) && (__riscv_xlen == 64)
+#define SCUDO_RISCV64 1
+#else
+#define SCUDO_RISCV64 0
+#endif
+
 #if defined(__LP64__)
 #define SCUDO_WORDSIZE 64U
 #else