diff --git a/src/boards/195.c b/src/boards/195.c
index f956a1a..730a6d7 100644
--- a/src/boards/195.c
+++ b/src/boards/195.c
@@ -20,7 +20,7 @@
 #include "mapinc.h"
 #include "mmc3.h"
 
-writefunc writePPU;
+static writefunc writePPU;
 static uint8 *CHRRAM;
 static uint32 CHRRAMSIZE;
 static uint8 mask;
diff --git a/src/boards/252_253.c b/src/boards/252_253.c
index de2c24f..06d3133 100644
--- a/src/boards/252_253.c
+++ b/src/boards/252_253.c
@@ -27,7 +27,7 @@ static uint8 mask;
 static uint8 compare;
 
 extern uint32 RefreshAddr;
-writefunc writePPU;
+static writefunc writePPU;
 
 static SFORMAT stateRegs[] ={
 	{ &mask, 1, "CHRM" },
diff --git a/src/boards/544.c b/src/boards/544.c
index ba29c5a..ec9eefe 100644
--- a/src/boards/544.c
+++ b/src/boards/544.c
@@ -29,7 +29,7 @@ static uint8 mask;
 static uint8 compare;
 
 extern uint32 RefreshAddr;
-writefunc writePPU;
+static writefunc writePPU;
 
 static SFORMAT stateRegs[] ={
         { nt, 4, "EXPN" },
diff --git a/src/boards/vrc2and4.h b/src/boards/vrc2and4.h
index 1cd19e8..0f3445a 100644
--- a/src/boards/vrc2and4.h
+++ b/src/boards/vrc2and4.h
@@ -17,9 +17,9 @@ extern signed short int VRC4_cycles;
 extern int    (*VRC24_GetPRGBank)(int);
 extern int    (*VRC24_GetCHRBank)(int);
 extern void   (*VRC24_Sync)();
-DECLFW((*VRC24_ExternalSelect));
-DECLFR((*VRC24_WRAMRead));
-DECLFW((*VRC24_WRAMWrite));
+extern DECLFW((*VRC24_ExternalSelect));
+extern DECLFR((*VRC24_WRAMRead));
+extern DECLFW((*VRC24_WRAMWrite));
 
 void VRC24_syncPRG    (int AND, int OR);
 void VRC24_syncCHR    (int AND, int OR);