-SRC_HC_OPTS += `$(GTK_CONFIG) --cflags` -optc-DRTS_GTK_FRONTPANEL
-else
-SRCS_RTS_C := $(filter-out Vis%.c, $(SRCS_RTS_C))
-endif
-
-VisCallbacks_CC_OPTS = -optc-Wno-unused
-
+SRC_HC_OPTS += `$(GTK_CONFIG) --cflags` -optc-DRTS_GTK_FRONTPANEL
+SRCS_RTS_C := $(SRCS_RTS_C) $(wildcard Vis*.c)
+VisCallbacks_CC_OPTS += -optc-Wno-unused
+endif # GhcRtsWithFrontPanel