diff --git a/libc/platform/bionic/tls_defines.h b/libc/platform/bionic/tls_defines.h
index 78099b3..3e2efa3 100644
--- a/libc/platform/bionic/tls_defines.h
+++ b/libc/platform/bionic/tls_defines.h
@@ -114,6 +114,28 @@
 #define TLS_SLOT_BIONIC_TLS       9
 #define MAX_TLS_SLOT              9 // update this value when reserving a slot
 
+#elif defined(__riscv)
+
+// RISC-V ELF Specification[1] specifies that RISC-V uses Variant I as described
+// by the ELF TLS specification, with tp containing the address one past the end
+// of the TCB.
+//
+// [1]: RISC-V ELF Specification. Section: Thread Local Storage
+// https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc#thread-local-storage
+
+#define MIN_TLS_SLOT             (-9) // update this value when reserving a slot
+
+#define TLS_SLOT_BIONIC_TLS      (-9)
+#define TLS_SLOT_DTV             (-8)
+#define TLS_SLOT_THREAD_ID       (-7)
+#define TLS_SLOT_APP             (-6)
+#define TLS_SLOT_OPENGL          (-5)
+#define TLS_SLOT_OPENGL_API      (-4)
+#define TLS_SLOT_STACK_GUARD     (-3)
+#define TLS_SLOT_SANITIZER       (-2)
+#define TLS_SLOT_ART_THREAD_SELF (-1)
+#define MAX_TLS_SLOT             (-1)
+
 #endif
 
 #define BIONIC_TLS_SLOTS (MAX_TLS_SLOT - MIN_TLS_SLOT + 1)