diff --git a/Makefile b/Makefile
index 4fa98fd0..30aa0315 100644
--- a/Makefile
+++ b/Makefile
@@ -240,9 +240,9 @@ else
 endif
 
 ifeq ($(BACKEND_AUDIO), SDL2)
-  SOURCES += src/Backends/Audio/SDL2.cpp
+  SOURCES += src/Backends/Audio/SDL2.cpp src/Backends/Audio/SoftwareMixer.cpp
 else ifeq ($(BACKEND_AUDIO), miniaudio)
-  SOURCES += src/Backends/Audio/miniaudio.cpp external/miniaudio.c
+  SOURCES += src/Backends/Audio/miniaudio.cpp src/Backends/Audio/SoftwareMixer.cpp
   CSE2_LIBS += -lm -lpthread
 
   ifneq ($(WINDOWS), 1)