diff --git a/src/hardware/iohandler.cpp b/src/hardware/iohandler.cpp
index 88448fdc..619808ec 100644
--- a/src/hardware/iohandler.cpp
+++ b/src/hardware/iohandler.cpp
@@ -404,6 +404,7 @@ Bitu IO_ReadB(Bitu port) {
 		entry->eip=reg_eip;
 		CPU_Push16(SegValue(cs));
 		CPU_Push16(reg_ip);
+		Bit8u old_al = reg_al;
 		Bit16u old_dx = reg_dx;
 		reg_dx = port;
 		RealPt icb = CALLBACK_RealPointer(call_priv_io);
@@ -415,6 +416,7 @@ Bitu IO_ReadB(Bitu port) {
 		iof_queue.used--;
 
 		retval = reg_al;
+		reg_al = old_al;
 		reg_dx = old_dx;
 		memcpy(&lflags,&old_lflags,sizeof(LazyFlags));
 		cpudecoder=old_cpudecoder;
@@ -441,6 +443,7 @@ Bitu IO_ReadW(Bitu port) {
 		entry->eip=reg_eip;
 		CPU_Push16(SegValue(cs));
 		CPU_Push16(reg_ip);
+		Bit16u old_ax = reg_ax;
 		Bit16u old_dx = reg_dx;
 		reg_dx = port;
 		RealPt icb = CALLBACK_RealPointer(call_priv_io);
@@ -452,6 +455,7 @@ Bitu IO_ReadW(Bitu port) {
 		iof_queue.used--;
 
 		retval = reg_ax;
+		reg_ax = old_ax;
 		reg_dx = old_dx;
 		memcpy(&lflags,&old_lflags,sizeof(LazyFlags));
 		cpudecoder=old_cpudecoder;
@@ -477,6 +481,7 @@ Bitu IO_ReadD(Bitu port) {
 		entry->eip=reg_eip;
 		CPU_Push16(SegValue(cs));
 		CPU_Push16(reg_ip);
+		Bit32u old_eax = reg_eax;
 		Bit16u old_dx = reg_dx;
 		reg_dx = port;
 		RealPt icb = CALLBACK_RealPointer(call_priv_io);
@@ -488,6 +493,7 @@ Bitu IO_ReadD(Bitu port) {
 		iof_queue.used--;
 
 		retval = reg_eax;
+		reg_eax = old_eax;
 		reg_dx = old_dx;
 		memcpy(&lflags,&old_lflags,sizeof(LazyFlags));
 		cpudecoder=old_cpudecoder;