diff --git a/Makefile.port b/Makefile.port
index 4c0e8dc2e..210f72e0c 100644
--- a/Makefile.port
+++ b/Makefile.port
@@ -116,7 +116,8 @@ DEFINES := \
   PAL=0 \
   PIRACYCHECKS=0 \
   ROM_SIZE=$(ROM_SIZE) \
-  _LANGUAGE_C=1
+  _LANGUAGE_C=1 \
+  GBI_FLOATS=1
 
 ifeq ($(DEBUG),1)
   DEFINES := $(DEFINES) DEBUG=1