diff --git a/External/ChemDraw/CMakeLists.txt b/External/ChemDraw/CMakeLists.txt
index dd26e23a2..54fe98dd8 100644
--- a/External/ChemDraw/CMakeLists.txt
+++ b/External/ChemDraw/CMakeLists.txt
@@ -119,11 +119,11 @@ if(RDK_BUILD_CHEMDRAW_SUPPORT)
   endif()
 
   if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-comment -Wno-parentheses -Wno-logical-op-parentheses -Wno-pointer-bool-conversion -Wno-unused-value -Wno-unsequenced -Wno-constant-logical-operand")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-comment -Wno-parentheses -Wno-logical-op-parentheses -Wno-pointer-bool-conversion -Wno-unused-value -Wno-unsequenced -Wno-constant-logical-operand")
   endif()
 
   if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wformat-overflow=0 -Wformat=0 -Wno-format-security")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wformat-overflow=0 -Wformat=0 -Wno-format-security")
   endif()
 
   include_directories(chemdraw)