diff --git a/evm/src/cpu/kernel/asm/core/syscall_stubs.asm b/evm/src/cpu/kernel/asm/core/syscall_stubs.asm
index 1530872c..1df96bd7 100644
--- a/evm/src/cpu/kernel/asm/core/syscall_stubs.asm
+++ b/evm/src/cpu/kernel/asm/core/syscall_stubs.asm
@@ -1,8 +1,19 @@
 // Labels for unimplemented syscalls to make the kernel assemble.
 // Each label should be removed from this file once it is implemented.
 
+// This is a temporary version that returns 0 on all inputs.
+// TODO: Fix this.
 global sys_blockhash:
-    PANIC
+    // stack: kexit_info, block_number
+    %charge_gas_const(@GAS_BLOCKHASH)
+    %stack (kexit_info, block_number) -> (kexit_info, 0)
+    EXIT_KERNEL
+
+// This is a temporary version that returns 0.
+// TODO: Fix this.
+// TODO: What semantics will this have for Edge?
 global sys_prevrandao:
-    // TODO: What semantics will this have for Edge?
-    PANIC
+    // stack: kexit_info
+    %charge_gas_const(@GAS_BASE)
+    %stack (kexit_info) -> (kexit_info, 0)
+    EXIT_KERNEL