diff --git a/reactos/lib/fast486/common.c b/reactos/lib/fast486/common.c
index 583720057fe..1a2bb09136b 100644
--- a/reactos/lib/fast486/common.c
+++ b/reactos/lib/fast486/common.c
@@ -32,6 +32,7 @@
 /* PUBLIC FUNCTIONS ***********************************************************/
 
 BOOLEAN
+FASTCALL
 Fast486ReadMemory(PFAST486_STATE State,
                   FAST486_SEG_REGS SegmentReg,
                   ULONG Offset,
@@ -156,6 +157,7 @@ Fast486ReadMemory(PFAST486_STATE State,
 }
 
 BOOLEAN
+FASTCALL
 Fast486WriteMemory(PFAST486_STATE State,
                    FAST486_SEG_REGS SegmentReg,
                    ULONG Offset,
diff --git a/reactos/lib/fast486/common.h b/reactos/lib/fast486/common.h
index 7bc04abfa84..b4a1b2ed288 100644
--- a/reactos/lib/fast486/common.h
+++ b/reactos/lib/fast486/common.h
@@ -137,6 +137,7 @@ C_ASSERT(sizeof(FAST486_PAGE_DIR) == sizeof(ULONG));
 /* FUNCTIONS ******************************************************************/
 
 BOOLEAN
+FASTCALL
 Fast486ReadMemory
 (
     PFAST486_STATE State,
@@ -148,6 +149,7 @@ Fast486ReadMemory
 );
 
 BOOLEAN
+FASTCALL
 Fast486WriteMemory
 (
     PFAST486_STATE State,
diff --git a/reactos/lib/fast486/fpu.c b/reactos/lib/fast486/fpu.c
index a9906447925..d7d5f6dcf63 100644
--- a/reactos/lib/fast486/fpu.c
+++ b/reactos/lib/fast486/fpu.c
@@ -1044,8 +1044,10 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeD8)
 {
     FAST486_MOD_REG_RM ModRegRm;
     BOOLEAN AddressSize = State->SegmentRegs[FAST486_REG_CS].Size;
+#ifndef FAST486_NO_FPU
     PFAST486_FPU_DATA_REG SourceOperand, DestOperand;
     FAST486_FPU_DATA_REG MemoryData;
+#endif
 
     TOGGLE_ADSIZE(AddressSize);
 
@@ -1692,9 +1694,11 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDA)
 {
     FAST486_MOD_REG_RM ModRegRm;
     BOOLEAN AddressSize = State->SegmentRegs[FAST486_REG_CS].Size;
+#ifndef FAST486_NO_FPU
     PFAST486_FPU_DATA_REG SourceOperand, DestOperand;
     LONG Value;
     FAST486_FPU_DATA_REG MemoryData;
+#endif
 
     TOGGLE_ADSIZE(AddressSize);
 
@@ -2013,8 +2017,10 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDC)
 {
     FAST486_MOD_REG_RM ModRegRm;
     BOOLEAN AddressSize = State->SegmentRegs[FAST486_REG_CS].Size;
+#ifndef FAST486_NO_FPU
     PFAST486_FPU_DATA_REG SourceOperand, DestOperand;
     FAST486_FPU_DATA_REG MemoryData;
+#endif
 
     TOGGLE_ADSIZE(AddressSize);
 
@@ -2389,7 +2395,9 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDE)
 {
     FAST486_MOD_REG_RM ModRegRm;
     BOOLEAN AddressSize = State->SegmentRegs[FAST486_REG_CS].Size;
+#ifndef FAST486_NO_FPU
     PFAST486_FPU_DATA_REG SourceOperand, DestOperand;
+#endif
 
     TOGGLE_ADSIZE(AddressSize);