diff --git a/CMakeLists.txt b/CMakeLists.txt
index a2f72106..469f03b4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -68,6 +68,7 @@ parse_Makefile_am(${CMAKE_CURRENT_SOURCE_DIR}/src/dec "WEBP_SRCS")
 parse_Makefile_am(${CMAKE_CURRENT_SOURCE_DIR}/src/demux "WEBP_SRCS")
 parse_Makefile_am(${CMAKE_CURRENT_SOURCE_DIR}/src/dsp "WEBP_SRCS")
 parse_Makefile_am(${CMAKE_CURRENT_SOURCE_DIR}/src/enc "WEBP_SRCS")
+parse_Makefile_am(${CMAKE_CURRENT_SOURCE_DIR}/src/mux "WEBP_SRCS")
 parse_Makefile_am(${CMAKE_CURRENT_SOURCE_DIR}/src/utils "WEBP_SRCS")
 
 # Remove the files specific to SIMD we don't use.