diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5437f20c0d..8f03f2c7dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -28,9 +28,6 @@ set(WITH_ASM "auto" CACHE STRING "Specify assembly optimizations to use (x86_64|
 set(WITH_FIELD "auto" CACHE STRING "Specify Field Implementation (64bit|32bit|auto).")
 set(WITH_SCALAR "auto" CACHE STRING "Specify scalar implementation (64bit|32bit|auto).")
 
-#TODO: add this option to Conan Scripts
-#set(WITH_BIGNUM "auto" CACHE STRING "Specify Bignum Implementation (gmp|no|auto).")
-
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 
 include(Secp256k1Tools)
@@ -96,24 +93,6 @@ elseif (NOT WITH_FIELD STREQUAL "32bit")
   message(FATAL_ERROR "Invalid scalar implementation: ${WITH_SCALAR}")
 endif()
 
-## Implement --with-bignum
-##------------------------------------------------------------------------------
-#if (WITH_BIGNUM STREQUAL "auto")
-#  _check_has_gmp()
-#  if (HAS_GMP)
-#    set(WITH_BIGNUM "gmp")
-#  else()
-#    set(WITH_BIGNUM "no")
-#  endif()
-#elseif (WITH_BIGNUM STREQUAL "gmp")
-#  _check_has_gmp()
-#  if (NOT HAS_GMP)
-#    message(FATAL_ERROR "gmp bignum explicitly requested but libgmp not available")
-#  endif()
-#elseif (NOT WITH_BIGNUM STREQUAL "no")
-#  message(FATAL_ERROR "Invalid bignum implementation: ${WITH_BIGNUM}")
-#endif()
-
 # Build
 #==============================================================================
 add_library(secp256k1 STATIC
@@ -154,20 +133,16 @@ elseif (WITH_SCALAR STREQUAL "32bit")
 endif()
 
 
-
-#TODO(fernando): See how to add this compile_definitions in the Conan Script
-#if (WITH_BIGNUM STREQUAL "gmp")
+if (WITH_BIGNUM STREQUAL "gmp")
   target_compile_definitions(secp256k1 PUBLIC -DHAVE_LIBGMP=1)
   target_compile_definitions(secp256k1 PUBLIC -DUSE_NUM_GMP=1)
   target_compile_definitions(secp256k1 PUBLIC -DUSE_FIELD_INV_NUM=1)
   target_compile_definitions(secp256k1 PUBLIC -DUSE_SCALAR_INV_NUM=1)
-#  target_include_directories(secp256k1 PUBLIC ${GMP_INCLUDE_DIR})
-#  target_link_libraries(secp256k1 ${GMP_LIBRARIES})
-#elseif (WITH_BIGNUM STREQUAL "no")
-#  target_compile_definitions(secp256k1 PUBLIC -DUSE_NUM_NONE=1)
-#  target_compile_definitions(secp256k1 PUBLIC -DUSE_FIELD_INV_BUILTIN=1)
-#  target_compile_definitions(secp256k1 PUBLIC -DUSE_SCALAR_INV_BUILTIN=1)
-#endif()
+elseif (WITH_BIGNUM STREQUAL "no")
+  target_compile_definitions(secp256k1 PUBLIC -DUSE_NUM_NONE=1)
+  target_compile_definitions(secp256k1 PUBLIC -DUSE_FIELD_INV_BUILTIN=1)
+  target_compile_definitions(secp256k1 PUBLIC -DUSE_SCALAR_INV_BUILTIN=1)
+endif()
 
 target_link_libraries(secp256k1 PUBLIC ${CONAN_LIBS})
 
diff --git a/conanfile.py b/conanfile.py
index 1ff394fbe2..05da0b0c1f 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -14,17 +14,18 @@ class Secp256k1Conan(ConanFile):
     build_policy = "missing"
     exports_sources = "src/*", "include/*", "CMakeLists.txt", "cmake/*", "secp256k1Config.cmake.in", "contrib/*", "test/*"
 
-    # package_files = "build/lsecp256k1.a"  #TODO!
-
-    # requires = (("gmp/6.1.2@bitprim/stable"))
-
     def build_requirements(self):
         if self.settings.os == "Linux" or self.settings.os == "Macos":
             self.build_requires("gmp/6.1.2@bitprim/stable")
 
     def build(self):
         cmake = CMake(self)
-        cmake.configure(source_dir=self.conanfile_directory)
+        cmake_args = {}
+        if self.settings.os == "Windos":
+            cmake_args = {"-DWITHBIGNUM=no"}
+        else:
+            cmake_args = {"-DWITHBIGNUM=gmp"}
+        cmake.configure(source_dir=self.conanfile_directory, args=cmake_args)
         cmake.build()
 
     def package(self):