diff --git a/Makefile.dmd b/Makefile.dmd
index 24a1d06..7c1b7c2 100644
--- a/Makefile.dmd
+++ b/Makefile.dmd
@@ -3,7 +3,7 @@ COMFLAGS=
 DLINK=$(COMFLAGS) 
 VERSION=$(shell cat Version)
 DFLAGS=$(COMFLAGS) -I./src -J./src/c64 -J./src/font -O
-CFLAGS=$(COMFLAGS) -O1
+CFLAGS=$(COMFLAGS) -O1 -std=c99
 CXXFLAGS=-I./src -O3
 COMPILE.d = $(DC) $(DFLAGS) -c -of$@
 OUTPUT_OPTION=
@@ -21,7 +21,7 @@ $(TARGET): $(C64OBJS) $(OBJS) $(CXX_OBJS)
 	$(CXX) $(CXXFLAGS) -c $< -o $@
 
 .c.o : $(C_SRCS)
-	$(CC) -c $< -o $@
+	$(CC) $(CFLAGS) -c $< -o $@
 
 ct: $(C64OBJS) $(CTOBJS)
 
diff --git a/Makefile.ldc b/Makefile.ldc
index b89077a..a6c4714 100644
--- a/Makefile.ldc
+++ b/Makefile.ldc
@@ -6,7 +6,7 @@ LIBS=-L-ldl -L-lstdc++
 COMFLAGS=-O2
 VERSION=$(shell cat Version)
 DFLAGS=$(COMFLAGS) -I./src -J./src/c64 -J./src/font
-CFLAGS=$(COMFLAGS)
+CFLAGS=$(COMFLAGS) -std=c99
 CXXFLAGS=$(COMFLAGS) -I./src 
 COMPILE.d = $(DC) $(DFLAGS) -c
 DC=ldc2
@@ -28,7 +28,7 @@ ccutter:$(C64OBJS) $(OBJS) $(CXX_OBJS)
 	$(CXX) $(CXXFLAGS) -c $< -o $@
 
 .c.o : $(C_SRCS)
-	$(CC) -c $< -o $@
+	$(CC) $(CFLAGS) -c $< -o $@
 
 ct: $(C64OBJS) $(CTOBJS)