diff --git a/Makefile b/Makefile
index 110d5f4..80a2ea0 100644
--- a/Makefile
+++ b/Makefile
@@ -163,7 +163,7 @@
 HOST_LDXX = $(LDXX)
 
 CPPFLAGS += $(CPPFLAGS_$(CONFIG))
-DEFINES += $(DEFINES_$(CONFIG))
+DEFINES += $(DEFINES_$(CONFIG)) INSTALL_PREFIX=\"$(prefix)\"
 LDFLAGS += $(LDFLAGS_$(CONFIG))
 
 CFLAGS += -std=c89 -pedantic