diff --git a/CMakeLists.txt b/CMakeLists.txt
index 85c46ae0d1..8f68b957d7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -287,7 +287,7 @@ if(CMAKE_GENERATOR MATCHES "Make|Ninja")
   # guarantee that the flags appear at the end of the command line.
   set(SECP256K1_APPEND_CFLAGS "" CACHE STRING "Compiler flags that are appended to the command line after all other flags added by the build system. This variable is intended for debugging and special builds.")
   if(SECP256K1_APPEND_CFLAGS)
-    string(APPEND CMAKE_C_COMPILE_OBJECT " ${SECP256K1_APPEND_CFLAGS}")
+    string(REPLACE "<FLAGS>" "<FLAGS> ${SECP256K1_APPEND_CFLAGS}" CMAKE_C_COMPILE_OBJECT "${CMAKE_C_COMPILE_OBJECT}")
   endif()
 
   set(SECP256K1_APPEND_LDFLAGS "" CACHE STRING "Linker flags that are appended to the command line after all other flags added by the build system. This variable is intended for debugging and special builds.")