diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6c2a5a84..3d668fcb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -182,7 +182,7 @@ target_include_directories(fmt PUBLIC
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
   $<INSTALL_INTERFACE:include>)
 
-set(FMT_DEBUG_POSTFIX d)
+set(FMT_DEBUG_POSTFIX d CACHE STRING "Debug library postfix.")
 
 set_target_properties(fmt PROPERTIES
   VERSION ${FMT_VERSION} SOVERSION ${CPACK_PACKAGE_VERSION_MAJOR}