diff --git a/build/defaults.mak b/build/defaults.mak
index 6a4ad3e0b..2b3d8f085 100644
--- a/build/defaults.mak
+++ b/build/defaults.mak
@@ -2,7 +2,7 @@ HOSTCC = gcc
 HOSTCXX = g++
 PYTHON = python3
 
-SFLAGS += -DDEBUG=$(DEBUG)
+SFLAGS = -DDEBUG=$(DEBUG)
 SFLAGS += -DEPSILON_GETOPT=$(EPSILON_GETOPT)
 SFLAGS += -DEPSILON_TELEMETRY=$(EPSILON_TELEMETRY)
 SFLAGS += -DESCHER_LOG_EVENTS_BINARY=$(ESCHER_LOG_EVENTS_BINARY)
@@ -13,9 +13,9 @@ CXXFLAGS = -std=c++11 -fno-exceptions -fno-rtti -fno-threadsafe-statics
 
 # Flags - Optimizations
 ifeq ($(DEBUG),1)
-SFLAGS = -O0 -g
+SFLAGS += -O0 -g
 else
-SFLAGS = -Os
+SFLAGS += -Os
 endif
 
 # Flags - Header search path