diff --git a/src/bignum.h b/src/bignum.h
index 5ec3544..c385f22 100644
--- a/src/bignum.h
+++ b/src/bignum.h
@@ -49,7 +49,6 @@
 
   void AssignPowerUInt16(uint16_t base, int exponent);
 
-  void AddUInt16(uint16_t operand);
   void AddUInt64(uint64_t operand);
   void AddBignum(const Bignum& other);
   // Precondition: this >= other.