--- feh-2.6.2/config.mk
+++ feh-2.6.2/config.mk
@@ -32,7 +32,7 @@
 endif
 
 ifeq (${debug},1)
-	CFLAGS += -DDEBUG -O0
+	CFLAGS += -DDEBUG
 	MAN_DEBUG = . This is a debug build.
 else
 	MAN_DEBUG =
