diff --git a/evm/src/cpu/kernel/asm/bignum/ge.asm b/evm/src/cpu/kernel/asm/bignum/ge.asm
index cdd7712f..e7f5aca2 100644
--- a/evm/src/cpu/kernel/asm/bignum/ge.asm
+++ b/evm/src/cpu/kernel/asm/bignum/ge.asm
@@ -1,7 +1,8 @@
 // Arithmetic on little-endian integers represented with 128-bit limbs.
 // All integers must be under a given length bound, and are padded with leading zeroes.
 
-// Returns a >= b.
+// Compares two bignums of the same given length. Assumes that len > 0.
+// Returns 1 if a > b, 3 if a == b, and 0 if a < b.
 global ge_bignum:
     // stack: len, a_start_loc, b_start_loc, retdest
     SWAP1
diff --git a/evm/src/cpu/kernel/asm/bignum/iszero.asm b/evm/src/cpu/kernel/asm/bignum/iszero.asm
index ff755270..2f742f77 100644
--- a/evm/src/cpu/kernel/asm/bignum/iszero.asm
+++ b/evm/src/cpu/kernel/asm/bignum/iszero.asm
@@ -3,6 +3,10 @@
 
 global iszero_bignum:
     // stack: len, start_loc, retdest
+    DUP1
+    // stack: len, len, start_loc, retdest
+    ISZERO
+    %jumpi(eqzero)
     DUP2
     // stack: start_loc, len, start_loc, retdest
     ADD