diff --git a/lang/m2/m2mm/Makefile b/lang/m2/m2mm/Makefile
index e2cbf9e69..7f2774789 100644
--- a/lang/m2/m2mm/Makefile
+++ b/lang/m2/m2mm/Makefile
@@ -16,7 +16,7 @@ PROFILE =
 M2COMPILER = m2
 DEFDIR = lib/m2
 HOMEDIR =
-CFLAGS = -O $(PROFILE) $(INCLUDES) -DSTATIC= -DM2COMPILER=\"$(M2COMPILER)\" -DDEF_DIR=$(DEFDIR) $(HOMEDIR)
+CFLAGS = -O $(PROFILE) $(INCLUDES) -DSTATIC= -DM2COMPILER=\"$(M2COMPILER)\" -DDEF_DIR=\"$(DEFDIR)\" $(HOMEDIR)
 LINTFLAGS = -DSTATIC= -DNORCSID
 MALLOC = $(LIBDIR)/malloc.o
 LDFLAGS = -i $(PROFILE)